Srs enhancements for coherent joint transmissions

ABSTRACT

Disclosed are systems and methods for enhancing sounding resource signal (SRS) communications. In some embodiments, power control parameters and/or spatial relation information is determined prior to transmissions of the SRS signal. The determination may include a dynamic determination or a selection of a power control parameter set from a plurality of power control parameter sets. In some embodiments, cross-SRS interference is reduced when multiple transmissions utilize a same resource by applying orthogonal cover codes (OCC) to the resources prior to transmission.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. Nos. 63/299,789, 63/338,609, 63/407,856, and 63/419,246, which were filed in the U.S. Patent and Trademark Office on Jan. 14, 2022, May 5, 2022, Sep. 19, 2022, and Oct. 25, 2022, respectively, the entire contents of each of which are incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates generally to wireless communication systems, and more particularly, to improvements to sounding reference signal (SRS) enhancements in wireless communication systems.

SUMMARY

In the third generation partnership project (3GPP) framework, joint transmission (JT) may be categorized into coherent JT (CJT) and non-coherent JT (NCJT).

FIG. 1 illustrates an example of a CJT scheme 100, according to the prior art. In FIG. 1 , the CJT is based on the assumption that a base station or gNode B (gNB) in the cooperation set of a first transmission and reception point (TRP) 101 and a second TRP 102 has detailed CSI of the serving links from all cooperating TRPs to the same user equipment (UE) 103. In this manner, each of the TRPs 101 and 102 in the cooperation set may jointly transmit the same message to the UE 103 on the same time and frequency resources. The transmitted signals from different TRPs may be jointly precoded with prior information indicating phase synchronization across TRPs to achieve coherent combining at the served UE 103.

With employment of a centralized radio access network (C-RAN) architecture in real networks, the demand for CJT multi-TRP transmission has increased, thereby requiring some enhancement of the current fifth generation (5G) codebook design and CSI reporting framework to increase the feasibility of joint precoding among the TRPs in a cooperation set.

CSI Measurement and Reporting for CJT Multiple TRP (mTRP) Targeting Frequency Division Duplexing (FDD)

In practical CJT deployments, a gNB should be able to dynamically switch between CJT and single TRP transmission depending on traffic conditions and channel quality. This may include independent CSI measurement and reporting for each TRP as well as a joint CSI measurement and reporting for CJT multi-TRP transmission. Following current CSI measurement and reporting framework where CSI configuration and triggering for different TRPs are independent, CJT multi-TRP transmission may require three transmission hypotheses, where hypothesis 1 is a single TRP transmission with TRP1, hypothesis 2 is a single TRP transmission with TRP2, and hypothesis 3 is CJT of both TRP1 and TRP2.

The number of CSI reports in a bandwidth part (BWP) may be limited by UE capability that is up to 4 per time-domain behavior. CSI measurement and reporting of CJT transmission based on a current specification would consume a significant amount of UE capabilities for CSI, even for a two-TRP scenario. A CSI reporting delay is also significantly large due to the multiple measurement and reporting events. Therefore, a need in the art persists to avoid large signaling overhead and UE complexity.

In 3GPP release 17 (Rel. 17), dynamic channel/interference hypotheses CSI measurement and reporting were discussed and introduced for NCJT transmissions. For CSI enhancement for NCJT multi-TRP transmission, a total of three dynamic hypotheses were considered (i.e. two corresponding to single TRP transmissions and one corresponding to NCJT multi-TRP transmission) while CSI reporting associated with these measurement hypotheses may be configured by a single CSI reporting setting. For a CSI measurement associated to this single reporting setting, a UE may be configured with one CSI-RS resource set including K_(s)≥2 nonzero part (NZP) CSI-resource setting resources as channel measurement resources (CMR) for the single TRP measurement hypotheses and N≥1 NZP CSI-RS resource pairs (where each pair may be used as one CMR) for an NCJT measurement hypothesis. All CMR resources in the set may have the same number of ports and association of different TRPs (i.e. transmission control information (TCI) states) to these CMRs may be handled at the resource level. To do so, a UE may be configured with two CMR groups corresponding to two TRPs, where K_(s)=K₁+K₂, K₁ and K₂ are the number of CMRs in first and second groups, respectively. CMR pairs for NCJT measurement hypothesis may be determined by selection of one resource per CMR group.

In NCJT multi-TRP transmission, one possible option for CSI reporting is that the UE may be configured to report X=0, 1, 2 CSIs associated with the single-TRP measurement hypotheses and one CSI associated with an NCJT measurement hypothesis. If X=1, one CSI may be associated with the best single-TRP measurement, and if X=2, two CSIs may be associated with two different single-TRP measurements. That is, there are two single TRP measurements associated to a CSI-RS measurement transmitted from one specific TRP in an NCJT transmission with two TRPs. The best measured CSI among these two is chosen and reported when X=1.

Alternatively, a UE can be configured to report only one CSI associated with the best one among NCJT and single-TRP measurement hypotheses. That is, there are three total CSI measurements, one NCJT transmission (two TRP transmit CSI-RS signals) and two single TRP transmissions, one of which transmits the CSI-RS signal. The best measured CSI among these three CSI measurements is chosen and reported. For the NCJT measurement hypothesis, a UE may be expected to report two rank indicators (RIs), two precoding matrix indicators (PMIs), two lawful intercepts (Lis) and one channel quality indicator (CQI) per codeword, for single-DCI based NCJT when the maximal transmission layers are less than or equal to four.

With employment of C-RAN architecture in real networks and faced with rapid increasing demand for CJT multi-TRP transmission, some additional enhancements of CSI measurement and reporting framework may be required for CJT multi-TRP transmissions. Following the same approach as in Rel. 17 CSI enhancement for NCJT, CSI reporting overhead in CJT multi-TRP transmission can be addressed by associating CSI reporting of the three measurement hypotheses of CJT multi-TRP transmission with a single CSI reporting setting. For a CSI measurement associated to this single reporting setting, a UE can be configured with one CSI-RS resource set including K_(s)≥2 NZP CSI-RS resources as CMRs for the single TRP measurement hypotheses and N≥1 NZP CSI-RS resource pairs as CMRs for the CJT measurement hypothesis. All CMR resources in the set may have the same number of ports and association of different TCI states to these CMRs may be performed at the resource level. To do so, a UE may be configured with two CMR groups corresponding to two TRPs, where K_(s)=K₁+K₂, K₁ and K₂ are the number of CMRs in first and second groups, respectively. CMR pairs for the CJT measurement hypothesis may be determined by selection of one resource per CMR group. Based on gNB configuration and UE capability, the two single TRP CMR transmissions may be used for both measurements of the single TRP hypotheses as well as the CJT hypothesis.

Another approach may be that a UE may be configured with one CSI-RS resource set including K_(s)≥2 NZP CSI-RS resources each with one port group as CMRs for the single TRP measurement hypothesis and N≥1 pairs of NZP CSI-RS resources for the CJT measurement hypothesis. A UE may be configured with two port groups corresponding to two TRPs, where K₁ and K₂ are the number of CMRs in first and second port groups, respectively, and K_(s)=K₁+K₂. Association of different TCI states to these CMRs may be performed at the port group level where each port group is associated with one distinct TRP/TCI state. The CMR pairs for the CJT measurement hypothesis may be determined by selection of one resource per port group whereas each pair can be used as one CMR for the CJT measurement hypothesis. In this scheme, based on a gNB configuration and UE capability, the two single TRP CMR transmissions may be used for both measurements of the single TRP hypotheses as well as the CJT hypothesis.

Another alternative is that a single CSI reporting setting may be configured with two NZP CSI-RS resources resource sets. The first set may correspond to the single TRP measurement hypotheses and the second set may correspond to the CJT multi-TRP measurement hypothesis. The first resource set may include a total of K_(s) NZP CSI-RS resources, each with one TCI state corresponding to a single TRP transmission. The second resource set may include a total of N NZP CSI-RS resources corresponding to CJT transmission from both TRPs where each CMR resource is configured with two TCI states. It is noted that the number of ports of resources in the second set may be two times the number of ports of resources in the first set. In one gNB implementation, a CMR in the second set may be seen as the concatenation of two resources of the first set with different TCI states such that the same measurements of the single TRP transmission hypotheses would be allowed to be used for the CJT measurement hypothesis. The association of TCI states to the resources in the second set can be handled based on a definition of resource/port groups (i.e. in a concatenated version) or in general in a port-wise manner.

For a CJT measurement hypothesis, a UE may be expected to report one RI, one PMI, one LI and one CQI per codeword. In this case, the PMI selection for the CJT hypothesis would be based on a multi-panel codebook design requiring an enhancement of the current 5G codebook design framework to enable joint precoding among the TRPs in a cooperation set. Specifically, in 5G new radio (NR), the two types of codebooks having been specified are Type I and Type II. The Type I multi panel codebook design in the current specification can support CJT multi-TRP transmission and one PMI reporting in the CJT measurement hypothesis. However, this multi-panel codebook design is based on an assumption that different panels are quasi co-located and experience similar long term channel characteristics. This assumption is inapplicable to, and therefore, unrealistic for distributed multiple input multiple output (MIMO) scenarios. Moreover, the current Type II codebook design does not address multi-panel and multi-TRP transmission scenarios.

As such, there is a need in the art for an update to the codebook designs to increase the feasibility of joint precoding among the TRPs in a cooperation set.

Sounding Reference Signal (SRS)

A Sounding Reference Signal (SRS) is an uplink reference signal that is transmitted by a UE to a gNB. SRS transmission can provide information about multipath fading, scattering, Doppler, and power loss of a transmitted signal and assist the gNB in estimating the channel quality and managing further resource scheduling, beam management, and power control of the transmitted signal.

A UE may be allocated with a specific Zadoff-Chu (ZC) sequence to transmit an SRS, where the length of the sequence is equal to number of allocated resource elements for the SRS transmission. In some implementations, the UE can be configured to transmit an SRS from one, two, or four antenna ports in a comb structure across up to 14 symbols in each slot. The ZC sequence has constant modulus in the frequency domain in order to generate orthogonal versions of the allocated sequence by applying specific cyclic shifts to the sequence. These orthogonal sequences may then be used for transmission across different antenna ports sharing the same time and frequency resources. For example, four cyclic shifts are applied to the allocated ZC sequence to create four orthogonal sequences for four one-port SRS transmissions over four antenna ports that share the same resource elements.

An SRS allocated base sequence is r _(u,v)(n), where u∈{0, . . . , 29} is the group number and v is the base sequence number. Selection of u and v is based on a configured sequence identifier (ID), a sequence length, and a configured group/sequence hopping scheme. The cyclic shifted versions of the SRS sequence (for transmission across antenna ports) may be derived as shown in the equation below

r _(u,v) ^((α,δ))(n)=e ^(jαn) r _(u,v)(n), 0≤n<M

where M is the sequence length and the cyclic shift a may be derived using the following:

$\alpha = {\frac{2\pi}{n_{SRS}^{{CS},\max}}\left\lbrack {\left( {n_{SRS}^{CS} + \frac{n_{SRS}^{{CS},\max}\left( {p_{i} - 1000} \right)}{N_{ap}^{SRS}}} \right){mod}n_{SRS}^{{CS},\max}} \right\rbrack}$

where n_(SRS) ^(CS,max) is a maximum number of cyclic shifts, n_(SRS) ^(CS) is an allocated cyclic shift, pi is an antenna port number, and N_(ap) ^(SRS) is a number of allocated antenna ports. The values of n_(SRS) ^(CS,max), n_(SRS) ^(CS) and N_(ap) ^(SRS) may be radio resource control (RRC) configured. Allocation of SRS over frequency domain resources is in form of a nested tree structure to allow frequency hopping opportunities.

FIG. 4 illustrates an example of an SRS bandwidth configuration.

Referring to bandwidth configuration 400 of FIG. 4 , C_(SRS) determines a bandwidth on which a set of SRSs are defined. m_(SRS) specifies the number of RBs used for each of those SRS transmissions. The hopping parameters C_(SRS) and B_(SRS) (derived from Table 6.4.1.4.3-1 in TS 38.211) may be used to identify a nested tree structure of an SRS bandwidth, while K_(TC) is the transmission comb size.

The current specification approach for SRS interference suppression mainly relies on comb structure, frequency hopping, resource block (RB)-level partial frequency sounding (in Rel. 17) and SRS low correlation sequences (i.e., cyclic shifts of a ZC sequence). The increasing capacity demand and larger number of served UEs in New Radio (NR) has led to an increase in probability of SRS collisions. Additionally, as the SRS sequence correlation may be forced by a sequence length limitation, cross-SRS interference may become a bottleneck that degrades SRS performance. This problem is exacerbated in multi-TRP CJT scenarios.

In SRS transmissions, transmission power is determined by one or more power control parameters, such as UE transmit power P_(0_SRS,b,f,c)(q_(s)), fractional power control multiplier α_(SRS,b,f,c)(q_(s)) and pathloss reference signal q_(d). The power control parameters may be used to compute the SRS transmission power, such as through the following calculation:

$\begin{matrix} {\left. {P_{{SRS},b,f,c}\left( {i,q_{s},l} \right)} \right) = {\min\left\{ \begin{matrix} {P_{{CMAX},f,c}(i)} \\ \begin{matrix} {{P_{{0{\_ SRS}},b,f,c}\left( q_{s} \right)} + {10{\log\left( {2^{\mu}{M_{{SRS},b,f,c}(i)}} \right)}} +} \\ {{{\alpha_{{SRS},b,f,c}\left( q_{s} \right)}{{PL}_{b,f,c}\left( q_{d} \right)}} + {h_{b,f,c}\left( {i,l} \right)}} \end{matrix} \end{matrix} \right.}} &  \end{matrix}$

where b, f, c, i and q_(s) respectively present active bandwidth part, carrier, serving cell, transmission occasion and parameter set. P_(CMAX,f,c)(i) is configured UE transmit power, M_(SRS,b,f,c)(i) is number of SRS resource blocks, μ is subcarrier spacing and h_(b,f,c)(i, l) is closed loop power control component for state l.

Generally, the SRS power control parameters are configured for resource sets by Radio Resource Control (RRC). When the SRS power control parameters are pre-configured, the pre-selection of the power control parameters can lead to performance issues. For instance, if the power control parameters are RRC-configured based on the best TRP transmission, CSI acquisition performance may drastically degrade due to poor received signals at the other TRP. If power control parameters are RRC-configured based on the worst TRP transmission, there may be an increase in inter-TRP cross-SRS interference.

The present disclosure has been made to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below.

According to some embodiments of the present disclosure, one or more power control parameters are determined prior to transmission across TRPs. In some embodiments, the determined power control parameters are used to reconfigure SRS resource sets by updating some or all of the power control parameters. In some embodiments, the determined power control parameters are selected from a plurality of sets of power control parameters that are configured for the SRS resource set.

According to some embodiments of the present disclosure, inter-TRP cross-SRS interference is reduced with application of Orthogonal Cover Codes (OCC) to SRS resources that are shared among multiple UEs and/or multiple ports of a UE.

In an embodiment, a method comprises determining, at a user equipment (UE), that a Sounding Reference Signal (SRS) resource is to be transmitted to a base station (gNB); in response to determining that the SRS resource is to be transmitted to the gNB, determining one or more power control parameters of the SRS resource; and transmitting the SRS resource with the determined one or more power control parameters to the gNB.

In an embodiment, the method further comprises, in response to determining that the SRS resource is to be transmitted to the gNB, determining spatial relation information of the SRS resource.

In an embodiment, determining the one or more power control parameters of the SRS resource comprises determining a fractional power control multiplier.

In an embodiment, a nominal UE transmit power and a pathloss reference signal are configured for an SRS resource set that includes the SRS resource based on a worst transmission and reception point (TRP) transmission.

In an embodiment, determining the one or more power control parameters of the SRS resource comprises measuring a path loss for transmitting to the gNB and determining a pathloss reference signal from the measured path loss.

In an embodiment, determining the one or more power control parameters of the SRS resource comprises determining a nominal UE transmit power for a TRP transmission.

In an embodiment, a single pathloss reference signal and a single fractional power control multiplier are configured for an SRS resource set that includes the SRS resource.

In an embodiment, the method further comprises updating the one or more power control parameters using a medium access control (MAC) control element (MAC-CE) or dynamic control element (DCI).

In an embodiment, multiple options for the power control parameter are configured for an SRS resource set that includes the SRS resource and determining the one or more power control parameters of the SRS resource comprises selecting the power control parameter from the multiple options for the power control parameter that are configured for the resource set.

In an embodiment, the SRS resource is shared between a first TRP transmission and a second TRP transmission, and the UE applies an Orthogonal Cover Code (OCC) to the SRS to maintain orthogonality in use of the SRS resource between the first TRP transmission and the second TRP transmission.

In an embodiment, the first TRP transmission is sent from the UE to a particular TRP and the second TRP transmission is sent from a second UE to the particular TRP.

In an embodiment, a third TRP transmission sent is sent from the UE to a second TRP, the third TRP transmission is sent using a second resource comprising a same SRS base sequence as the SRS resource, and a cyclic shift is applied to the SRS base sequence for the third transmission such that the second resource and the SRS resource are orthogonal.

In an embodiment, a third TRP transmission sent is sent from the UE to a second TRP, and the third TRP transmission is sent using a second resource comprising a different SRS base sequence as the SRS resource.

In an embodiment, a third TRP transmission sent is sent from the UE to a second TRP, the third TRP transmission is sent using the SRS resource, and a comb structure, frequency hopping, or resource block-level partial frequency sounding structure is used to provide orthogonality between the third TRP transmission and the first TRP transmission.

In an embodiment, the first TRP transmission is sent from the UE to a first TRP and the second TRP transmission is sent from the UE to a second TRP.

In an embodiment, the UE applies the OCC to the SRS in response to receiving an indication from the gNB.

In an embodiment a method comprises determining, at a gNB that a plurality of TRP transmissions from one or more UEs are using a particular SRS resource; and in response to determining that the plurality of TRP transmissions from the one or more UEs are using the same resource, sending an indication to the one or more UEs which causes the one or more UEs to apply an orthogonal cover code (OCC) to the plurality of TRP transmissions.

In an embodiment, the plurality of TRP transmissions comprise a first TRP transmission from a first UE of the one or more UEs to a first TRP and a second TRP transmission from a second UE of the one or more UEs to the first TRP.

In an embodiment, a third TRP transmission from the first UE of the one or more UEs to a second TRP uses a second SRS resource comprising a same SRS base sequence as the particular SRS resource, and a cyclic shift is applied to the SRS base sequence for the third transmission such that the second SRS resource and the particular SRS resource orthogonal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certain embodiments of the present disclosure will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates an example of a CJT scheme 100;

FIG. 2 illustrates the indication of beams for each of two channels;

FIG. 3 illustrates the indication of beams for each of two channels, according to an embodiment;

FIG. 4 illustrates an example of an SRS bandwidth configuration;

FIG. 5 depicts an example of a multi-TRP scenario where each UE utilizes a plurality of resources to perform the multi-TRP transmissions;

FIG. 6 depicts an example application of OCC codes;

FIG. 7 depicts an example of a multi-TRP scenario where each UE utilizes a single SRS base sequence to perform the multi-TRP transmissions;

FIG. 8 depicts an example application of OCC codes (system 800 comprises two UEs, each with a comb size of two);

FIG. 9 depicts an example method for SRS transmissions;

FIG. 10 is a block diagram of an electronic device in a network environment, according to an embodiment; and

FIG. 11 shows a system including a UE and a gNB in communication with each other.

DETAILED DESCRIPTION

Embodiments of the disclosure will be described herein below with reference to the accompanying drawings. However, the embodiments of the disclosure are not limited to the specific embodiments and should be construed as including all modifications, changes, equivalent devices and methods, and/or alternative embodiments of the present disclosure. Descriptions of well-known functions and/or configurations will be omitted for the sake of clarity and conciseness.

The expressions “have,” “may have,” “include,” and “may include” as used herein indicate the presence of corresponding features, such as numerical values, functions, operations, or parts, and do not preclude the presence of additional features. The expressions “A or B,” “at least one of A or/and B,” or “one or more of A or/and B” as used herein include all possible combinations of items enumerated with them. For example, “A or B,” “at least one of A and B,” or “at least one of A or B” indicate (1) including at least one A, (2) including at least one B, or (3) including both at least one A and at least one B.

Terms such as “first” and “second” as used herein may modify various elements irrespective of an order and/or importance of the corresponding elements, and do not limit the corresponding elements. These terms may be used for the purpose of distinguishing one element from another element. For example, a first user device and a second user device may indicate different user devices irrespective of the order or importance. A first element may be referred to as a second element without departing from the scope the disclosure, and similarly, a second element may be referred to as a first element.

When a first element is “operatively or communicatively coupled with/to” or “connected to” another element, such as a second element, the first element may be directly coupled with/to the second element, and there may be an intervening element, such as a third element, between the first and second elements. To the contrary, when the first element is “directly coupled with/to” or “directly connected to” the second element, there is no intervening third element between the first and second elements.

All of the terms used herein including technical or scientific terms have the same meanings as those generally understood by an ordinary skilled person in the related art unless they are defined otherwise. The terms defined in a generally used dictionary should be interpreted as having the same or similar meanings as the contextual meanings of the relevant technology and should not be interpreted as having ideal or exaggerated meanings unless they are clearly defined herein. According to circumstances, even the terms defined in this disclosure should not be interpreted as excluding the embodiments of the disclosure.

The following discloses refinement of the codebook design framework targeting one PMI reporting in hypothesis 3 of the CJT multi-TRP transmission.

In this scheme, CSI reporting can follow the same approach as introduced for NCJT multi-TRP transmission in Rel. 17. That is, one CSI reporting triggering state would trigger X+1 CSIs, where X=0, 1, 2 CSIs are associated with the single-TRP measurement hypotheses and one CSI is associated with the CJT measurement hypothesis. If X=1, one CSI may be associated with the best single-TRP measurement, and if X=2, two CSIs may be associated with two different single-TRP measurements. A UE can be alternatively configured to report one CSI associated with the best one among CJT and single-TRP measurement hypotheses. In such a case, CSI can implicitly identify whether a reported CSI corresponds to a single-TRP CSI hypothesis or a CJT CSI hypothesis. The bitwidth associated to X+1 CSI reports may be given as Ceil(log₂N) for X=0, Ceil(log₂N)+Ceil(log₂K_(s)) for X=1, and Ceil(log₂N)+Ceil(log₂K₁)+Ceil(log₂K₂) for X=2.

Further disclosed herein is dynamic updating of TCI states of port groups in CMRs and/or CMR resources of the CJT measurement hypothesis through a MAC-CE or DCI indication.

RAN 1 has agreed to support CJT multi TRP transmission with up to four TRPs/TRP groups with equal priority. The CJT measurement hypothesis would, however, be based on N cooperating TRPs/TRP groups where the value of N can be selected and reported by the UE. This requires the introduction of a new UE capability that indicates how many CSIs can be calculated by a UE corresponding to different CJT transmission hypotheses with a different number of cooperating TRPs/TRP groups assumptions. In such a case, to provide the best channel quality, a UE would calculate multiple CSIs for all/some different possible CJT measurement hypothesis and select the value of N based on the best CJT hypothesis and report the corresponding CSI to a gNB. Such a UE capability may be based on n CSIs, where n∈[1, 2, . . . , n_(max)]. The maximum value for n can be derived with assumption of a maximum total of M TRPs in CJT, as

${{\max(n)} = {n_{\max} = {\begin{pmatrix} M \\ 2 \end{pmatrix} + \ldots + \begin{pmatrix} M \\ M \end{pmatrix}}}},$

if not including a single TRP hypothesis, and as

${{\max(n)} = {n_{\max} = {\begin{pmatrix} M \\ 1 \end{pmatrix} + \ldots + \begin{pmatrix} M \\ M \end{pmatrix}}}},$

if including the single TRP hypothesis. With a total of M=4 TRPs in CJT, as agreed upon in RAN1, the maximum value for n is

${n_{\max} = {{\begin{pmatrix} 4 \\ 2 \end{pmatrix} + \begin{pmatrix} 4 \\ 3 \end{pmatrix} + \begin{pmatrix} 4 \\ 4 \end{pmatrix}} = 11}},$

if not including the single TRP hypothesis, and as

$\begin{matrix} {{n_{\max} = {{\begin{pmatrix} 4 \\ 1 \end{pmatrix} + \begin{pmatrix} 4 \\ 2 \end{pmatrix} + \begin{pmatrix} 4 \\ 3 \end{pmatrix} + \begin{pmatrix} 4 \\ 4 \end{pmatrix}} = {15}}},} &  \end{matrix}$

if including the single TRP hypothesis. Codebook Design Refinement for CJT mTRP Targeting FDD

The Type I codebook design is founded based on a long term evolution (LTE) codebook design to support a single user MIMO for both high and low order transmissions. The Type II codebook is, however, designed based on a specific mathematic approach to provide more accurate information on channel characteristics using more sophisticated precoding matrices to support a multi-user MIMO with up to two layers of transmission. Both Type I and Type II codebooks are constructed based on 2-dimensional (2D) discrete Fourier transform (DFT) based beams and PMI reporting of information on beam selection and co-phase combining between two polarizations. The Type II codebook additionally reports the information on wide-band and sub-band amplitude coefficients of the selected beams.

Specifically, all radiating antenna elements are associated with an electric and magnetic field in each location around the antenna. The electric field at any point can be represented as a vector represented in two dimensions by projecting it along the spherical unit vectors {circumflex over (ϕ)} and {circumflex over (θ)}. The electric field of an antenna in a given direction (ϕ, θ) in far-field should be fully represented as the two dimensional vector, F(ϕ, θ)=[F_(ϕ)(ϕ, θ) F_(θ)(ϕ, θ)]^(T) which is referred to as the polarization vector. F_(ϕ) and F_(θ) are field components in the direction {circumflex over (ϕ)} and {circumflex over (θ)}. The real-valued instantaneous field in RF frequency can thus be simply written as

{right arrow over (E)}(t, ϕ, θ)={circumflex over (ϕ)}|F_(ϕ)(ϕ, θ)|cos(ωt+kr+∠F_(ϕ)(ϕ, θ))+{circumflex over (θ)}|F_(θ)(ϕ, θ)|cos(ωt+kr+∠F_(θ)(ϕ, θ)) where ω represents the transmission frequency in hertz (Hz) and kr contributes as a constant phase offset as a function of distance.

In the Type I codebook, PMI reporting occurs in 2 stages. In stage 1, wideband information including beam selection, or beam group selection is reported, and in stage 2, sub-band information including beam selection from within a group and phase shift selection for co-phasing between polarizations, layers and antenna panels is reported. The Type I codebook design provides two solutions of single panel and multi panel designs where each supports a Mode 1 and Mode 2 of reporting operation. The Type II codebook design, however, is based on reporting the information of a beam selection set and then a set of amplitude and phase shift coefficients to generate a linearly weighted combination of those selected beams. The Type II codebook design provides two solutions of single panel and port selection designs. The Type II single panel solution relies on a hypothetical beam position using oversampling factors while the Type II port selection solution is based on a set of actual, beamformed CSI-RS transmissions.

Type I Multi-Panel Codebook Refinement for CJT mTRP Targeting FDD

In the Type I codebook, PMI reporting has dual stages of wideband and sub-band CSI reporting. In stage 1, long term channel characteristics such as beam selection or beam group selection is reported. In stage 2, short-term and frequency selective channel characteristics such as beam selection from within a group and phase shift selection for co-phasing between polarizations, layers and antenna panels is reported.

Currently, precoding matrices are defined based on a specific antenna configuration assumption at a gNB. These antenna configurations are specified by defining the number of cross polar antenna elements in each panel where N₁ is the number of cross polar antenna element columns and N₂ is the number of cross polar antenna element rows. The number of CSI-RS ports is derived by 2N₁N₂. With a definition of DFT oversampling for higher granularity for beam sweeping where O1 and O2 are oversampling factors in columns and rows, the number of candidate beams in the horizontal direction is defined as N₁O₁ and number of candidate beams in the vertical direction is defined as N₂O₂. Note that O₂ is set to one when N₂=1 (i.e., no beamforming in the vertical direction).

The Type I codebook design provides two solutions of single panel and multi panel designs, where each supports Mode 1 and Mode 2 of reporting operation. The operation mode is configured by radio resource control (RRC) parameter codebookMode to instruct a UE to apply a specific mode. In the Mode 1 operation for the Type I single panel codebook, the UE reports a specific beam selected from all candidate beams at stage 1 and a specific phase shift for cross polarized port groups at stage 2. The available values for phase shift of cross polarized port groups to select at stage 2 are [0, 90, 180, 270] for a single layer and [0, 90] for two layers with the same conceptual operation as a MIMO precoding for a two-port transmission scenario. In the Mode 2 operation for the Type I single panel codebook, the UE reports beam group selection at stage 1 and selection of a specific beam within the chosen beam group and a specific phase shift for cross polarized port groups at stage 2.

The i parameters are used by the UE to report channel state information to the gNB, where i_(1,1) indicates beam selection in the horizontal direction, i_(1,2) indicates beam selection in the vertical direction, i_(1,3) indicates a beam offset of multiple layers and i₂ indicates sub-band properties at stage 2 reporting. The beam offset uses values of multiple oversampling factors in either the horizontal and/or vertical direction to create spatial separation and relies on reflection and scattering.

The Type I multi panel codebook design supports configuration of either 2 or 4 antenna panels where the antenna elements configuration per panel is similarly defined as in the Type I single panel codebook. That is, the number of cross polar antenna element columns per panel is N₁, the number of cross polar antenna element rows per panel is N₂, and O1 and O2 are oversampling factors in columns and rows per panel. With N_(g) antenna panels, the number of CSI ports is derived as 2N_(g)N₁N₂, but the number of candidate beams are N₁O₁N₂O₂, meaning that the same beam is used for other polarizations and the other panels.

In the Mode 1 operation for the Type I multi panel codebook, the UE reports beam selection and wideband phase shift(s) for inter-panel co-phasing at stage 1 and one phase shift for sub-band inter-polarization co-phasing at stage 2. Mode 1 operation for the Type I multi panel codebook supports configuration of N_(g)=2 or N_(g)=4 antenna panels where for N_(g)=2 panels, one phase shift for inter-panel co-phasing is reported and for N_(g)=4 panels, three phase shifts are reported.

In the Mode 2 operation for the Type I multi panel codebook, the UE reports beam selection and two phase shifts for a combination of inter-panel and inter-polarization co-phasing at stage 1 and three phase shifts per sub-band combination of inter-panel and inter-polarization co-phasing at stage 2. Mode 2 operation for the Type I multi panel codebook supports the configuration of N_(g)=2 antenna panels.

The Type I multi panel codebook design, i_(1,1) indicates beam selection in the horizontal direction, i_(1,2) indicates beam selection in the vertical direction, i_(1,3) indicates beam offset of multiple layers, i_(1,4) is inter-panel co-phasing for Mode 1 while wideband combined inter-panel and inter-polarization co-phasing for Mode 2, and i₂ is sub-band combined inter-panel and inter-polarization co-phasing at stage 2 reporting.

The generation of precoding matrix for the Type I codebook is based on composition of beamforming (wideband precoder) and MIMO precoding (sub-band precoder) matrices where cross polarized port groups and multiple panels are assumed to share the same beam and beamforming virtualization coefficients. The inter-panel and inter-polarization co-phasing are included in MIMO precoding that reflects the short-term frequency selective channel information. In the current specification, the precoding matrix is defined in Equation (1) as follows.

W=W ₁ W ₂  (1)

where W₁ is the wideband beamforming precoder matrix and W₂ is the sub-band precoder matrix that are derived as follows. In the Type I single panel codebook design, the wideband beamforming precoder W₁ is defined in Equation (2) as follows.

$\begin{matrix} {W_{1} = \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix}} & (2) \end{matrix}$

where v_(l,m) are 2D DFT virtualization coefficients derived as v_(l,m)=x_(l)⊗u_(m) in Equations (3) and (4) as follows.

$\begin{matrix} {x_{i} = \begin{bmatrix} 1 & e^{\frac{j2\pi l}{N_{1}O_{1}}} & \ldots & e^{\frac{j2\pi{({N_{1} - 1})}l}{N_{1}O_{1}}} \end{bmatrix}} & (3) \end{matrix}$ $\begin{matrix} {u_{m} = \begin{bmatrix} 1 & e^{\frac{j2\pi l}{N_{2}O_{2}}} & \ldots & e^{\frac{j2\pi{({N_{2} - 1})}m}{N_{2}O_{2}}} \end{bmatrix}} & (4) \end{matrix}$

and sub-band precoder matrix W₂ is defined in Equation (5) as follows.

$\begin{matrix} {{W_{2} = {{\frac{1}{\sqrt{P}}\begin{bmatrix} 1 \\ \varphi_{n} \end{bmatrix}}{or}}}{\frac{1}{\sqrt{2P}}\begin{bmatrix} 1 & 1 \\ \varphi_{n} & {- \varphi_{n}} \end{bmatrix}}} & (5) \end{matrix}$

for a rank-1 or a rank-2 transmission where φ_(n) is the inter-polarization co-phasing.

In the Type I multi-panel codebook design, the wideband beamforming precoder matrix W₁ (for a two-panel scenario) is defined in Equation (6) as follows.

$\begin{matrix} {W_{1} = \begin{bmatrix} \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} & 0 \\ 0 & \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} \end{bmatrix}} & (6) \end{matrix}$

Sub-band precoder matrix W₂ design considers inter-panel co-phasing (i.e., φ_(p)) in addition to inter-polarization co-phasing (i.e. φ_(n)) as defined below in Equation (7) for a rank-1 or a rank-2 transmission.

$\begin{matrix} {W_{2} = {{\frac{1}{\sqrt{P_{{CSI} - {RS}}}}\begin{bmatrix} 1 \\ \varphi_{n} \\ \varphi_{p} \\ {\varphi_{n}\varphi_{p}} \end{bmatrix}}{or}{\frac{1}{\sqrt{2P_{{CSI} - {RS}}}}\begin{bmatrix} 1 & 1 \\ \varphi_{n} & {- \varphi_{n}} \\ \varphi_{p} & \varphi_{p} \\ {\varphi_{n}\varphi_{p}} & {{- \varphi_{n}}\varphi_{p}} \end{bmatrix}}}} & (7) \end{matrix}$

In the above codebook design, the priority of the precoder matrix design is to first consider cross polarization transmission and to then consider multi-beam transmission.

Further, there is a special design case in the current Type I single panel codebook design for rank-3 and rank-4 transmissions when antenna configuration can support more than 16 CSI-RS signals. In this case, antenna elements in the panel are divided into groups and a single beam is selected to be reused for transmission by each group of antenna elements with a different phase shift (i.e. θ_(p)) to provide differentiation. For a rank-3 transmission, the precoder matrix is defined in Equation (8) as follows.

$\begin{matrix} {W = {\frac{1}{\sqrt{3P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} \\ {\theta_{p}v_{l,m}} & {{- \theta_{p}}v_{l,m}} & {\theta_{p}v_{l,m}} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} \\ {\varphi_{n}\theta_{p}v_{l,m}} & {{- \varphi_{n}}\theta_{p}v_{l,m}} & {{- \varphi_{n}}\theta_{p}v_{l,m}} \end{bmatrix}}} & (8) \end{matrix}$

For rank-4 transmission, the precoder matrix is defined in Equation (9) as follows.

$\begin{matrix} {W = {\frac{1}{\sqrt{3P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} \\ {\theta_{p}v_{l,m}} & {{- \theta_{p}}v_{l,m}} & {\theta_{p}v_{l,m}} & {{- \theta_{p}}v_{l,m}} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} \\ {\varphi_{n}\theta_{p}v_{l,m}} & {{- \varphi_{n}}\theta_{p}v_{l,m}} & {{- \varphi_{n}}\theta_{p}v_{l,m}} & {\varphi_{n}\theta_{p}v_{l,m}} \end{bmatrix}}} & (9) \end{matrix}$

For the Type I codebook to address the CJT scenario, the current Type I multi-panel codebook design is based on an assumption that different panels are quasi co-located and experience similar long term channel characteristics that mainly involve wideband PMI information such as beam or beam group selection. As previously discussed, when there are N_(g) multiple panels (each with N₁N₂ ports), the number of beams available for selection is given by N₁O₁N₂O₂ and not by N_(g)N₁O₁N₂O₂, indicating that the same selected beam is reused for transmission from N_(g) panels. This assumption is inapplicable to, and thus, unrealistic for a distributed MIMO scenario in which multiple TRPs are not quasi co-located and each TRP may experience different long term channel characteristics requiring different beam/beam group selections per panel. That is, a different beam/beam group can be selected for each group of N₁N₂ antenna elements (i.e., each panel).

In this case, the present disclosure enables multiple beam selections at a first stage of PMI reporting for different panels. This can be performed by a separate indication of beams per panel using separate i parameters. As an example of such a scheme for a two-layer transmission over a two-panel multi-TRP scenario, the first stage of PMI reporting involves additionally introducing i_(1,k1), i_(1,k2) values for identification of the second panel beams or group of beams in the horizontal and vertical directions, respectively. These i_(1,k1), i_(1,k2) parameters can be any suitable values as long as their corresponding beams are spatially separated to rely on reflection and scattering.

Alternatively, and to reduce signaling overhead, the first stage of PMI reporting involves additionally introducing sets of i_(1,k) parameters for identification of the beams of other panels or group of beams in a similar approach as in the current specification. That is, the first layer beam in a panel is identified by its location in the horizontal and vertical directions while beams selected for other layers in that panel are identified by defining their offsets with respect to the first layer beam in that panel. For a two-layer transmission over the two panel multi-TRP scenario, i_(1,1) and i_(1,2) identify the first layer beam in the horizontal and vertical directions, i_(1,3) identifies an offset between the beams selected for each layer in the first panel as in the current specification, and then additionally introduced parameters i_(1,4), i_(1,5) specify the second panel's first layer beam in the horizontal and vertical directions, and i_(1,6) specifies a beam selected for other layer in the second panel with same approach as in the current specification by defining offset between the beams selected for each layer in the second panel. As previously discussed, beam offset only takes values of multiple oversampling factors in either the horizontal and/or vertical direction to create spatial separation to rely on reflection and scattering. This decreases the PMI signaling overhead by limiting the available position of selected beams or group of beams.

Alternatively, the first beam/beam group is indicated for the first layer of the first panel and beams of other panels are indicated using offset values from that first selected beam/beam group. The offset can be a multiple of oversampling factors in the horizontal or/and vertical directions. Since beam offset only takes values of multiple oversampling factors in either horizontal and/or vertical direction to create spatial separation and relies on reflection and scattering, the available positions of panels of the other beams are restricted with respect to the position of the first layer beam at the first panel. This significantly reduces signaling overhead but may degrade the overall performance depending on the environment. The offset may be zero, demoting this design to the current Type I multi-panel codebook design that all panels use the same beams/group of beams.

FIG. 2 illustrates the indication of beams for each of two channels, according to the prior art. In FIG. 2 , relating to the current specification, one reported beam can support up to rank two per panel (i.e. one cross polar beam per panel), and identical beam configurations 203, 204 are included per panel 201, 202, respectively.

FIG. 3 illustrates the indication of beams for each of two channels, according to an embodiment. In FIG. 3 , different beam configurations 303, 304 are included in the panels 301, 302. The embodiment shown in FIG. 3 is more practical for frequency range 2 (FR2) applications.

Specifically, in a scheme for a two-layer transmission over a two panel multi-TRP scenario, the first stage of PMI reporting involves additionally introducing is, for identification of the second panel beams or group of beams. That is, the first stage of PMI reporting provides values for i_(1,1) and i_(1,2) that identify the first layer beam or group of beams in the horizontal and vertical directions, a value for i_(1,3) that identifies an offset between the beams selected for each layer in the first panel, values for i_(1,4) and i_(1,5) that specify offsets between the beams selected for the first layer in the first panel and the beam of the first layer and the beam of the second layer in the second panel.

The current Type I multi-panel codebook design as illustrated in FIG. 2 considers reporting inter-panel co-phasing values (i.e., φ_(p)) in addition to inter-polarization co-phasing (i.e. φ_(n)) while inter-panel co-phasing is only used for coherent transmission of the same data from different panels. Similar to cross polarized transmission, the present disclosure introduces the use of MIMO precoding on different panels to provide short term frequency selective information of channel characteristics over different panels. To illustrate, in the current Type I multi panel codebook design, inter-panel co-phasing information is only used to achieve coherent combining of the same transmitted data from different panels at the UE.

With the introduction of MIMO precoding on panels, the number of required beams can be decreased for transmission of a specific rank compared to the current Type I multi-panel codebook illustrated in FIG. 2 . That is, each beam can now be used to provide up to a rank-2K transmission with K panels. In contrast to the NCJT scenario, embodiments of the disclosure achieve jointly precoded transmission with decreased CSI reporting overhead, particularly for high mobility scenarios where UE velocity combined with panels incoherency generates faster channel variations. In the high mobility NCJT scenario, the channel would rapidly change and more frequent NCJT CSI acquisition would be required, resulting in a rapid change of precoding matrices at each TRP. Thus, for a rank-R transmission with Mode 1, Equation (10) is derived as follows.

$\begin{matrix} {\text{?} = \left\{ {\begin{matrix} {{{\frac{1}{\sqrt{{RP}_{{CSI} - {RS}}}}\begin{bmatrix} \begin{bmatrix} \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} & 0 \\ 0 & \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} \end{bmatrix} & & 0 \\  & \ddots & \\ 0 & & \begin{bmatrix} \begin{bmatrix} \text{?} & 0 \\ 0 & \text{?} \end{bmatrix} & 0 \\ 0 & \begin{bmatrix} \text{?} & 0 \\ 0 & \text{?} \end{bmatrix} \end{bmatrix} \end{bmatrix}}C_{MIMO}{if}{mod}\left( {R,4} \right)} = 0} \\ {{{\frac{1}{\sqrt{{RP}_{{CSI} - {RS}}}}\begin{bmatrix} \begin{bmatrix} \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} & 0 \\ 0 & \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} \end{bmatrix} & & 0 \\  & \ddots & \\ 0 & & \begin{bmatrix} \begin{bmatrix} \text{?} & 0 \\ 0 & \text{?} \end{bmatrix} & 0 \\ 0 & \text{?} \end{bmatrix} \end{bmatrix}}C_{MIMO}{if}{mod}\left( {R,4} \right)} = 3} \\ {{{\frac{1}{\sqrt{{RP}_{{CSI} - {RS}}}}\begin{bmatrix} \begin{bmatrix} \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} & 0 \\ 0 & \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} \end{bmatrix} & & 0 \\  & \ddots & \\ 0 & & \begin{bmatrix} \text{?} & 0 \\ 0 & \text{?} \end{bmatrix} \end{bmatrix}}C_{MIMO}{if}{mod}\left( {R,4} \right)} = 2} \\ {{{\frac{1}{\sqrt{{RP}_{{CSI} - {RS}}}}\begin{bmatrix} \begin{bmatrix} \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} & 0 \\ 0 & \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} \end{bmatrix} & & 0 \\  & \ddots & \\ 0 & & \left\lbrack \text{?} \right\rbrack \end{bmatrix}}C_{MIMO}{if}{mod}\left( {R,4} \right)} = 1} \end{matrix}\text{?}\text{indicates text missing or illegible when filed}} \right.} & (10) \end{matrix}$

In Equation (10), v_(l,m) is 2D DFT virtualization coefficient of selected beam and C_(MIMO) is a MIMO precoding matrix over both panel and polarization that is defined in Equation (11) as follows.

C _(MIMO) =C _(polarization) ⊗C _(panel)  (11)

Depending on the value of R, C_(polarization) and C_(panel) are defined in Equations (12) and (13), respectively, as follows.

$\begin{matrix} {C_{polarization} = {\begin{bmatrix} 1 \\ \varphi_{n} \end{bmatrix}{{or}\begin{bmatrix} 1 & 1 \\ \varphi_{n} & {- \varphi_{n}} \end{bmatrix}}}} & (12) \end{matrix}$ $\begin{matrix} {C_{panel} = {\begin{bmatrix} {\begin{bmatrix} 1 \\ \varphi_{p_{1}} \end{bmatrix}} \\  \vdots \\ {\begin{bmatrix} 1 \\ \varphi_{p_{K - 1}} \end{bmatrix}} \end{bmatrix}{{or}\begin{bmatrix} \begin{bmatrix} 1 & 1 \\ \varphi_{p_{1}} & {- \varphi_{p_{1}}} \end{bmatrix} \\  \vdots \\ \begin{bmatrix} 1 & 1 \\ \varphi_{p_{K - 1}} & \varphi_{p_{K - 1}} \end{bmatrix} \end{bmatrix}}}} & (13) \end{matrix}$

where φ_(n) is the inter-polarization co-phasing and φ_(p) _(k) , k=1, . . . , K−1 is the inter-panel co-phasing for K panels with respect to the first panel where in the current specification, max(K)=4 for Mode 1. The above-disclosed scheme follows the same design foundation as in the special design case in the Type I single panel codebook for rank 3 and 4 with CSI-RS ports larger than 16. In this special design case, only one panel was included and the precoder matrix design priority was to first perform transmission over different groups of antenna elements and then perform cross polarization where the co-phasing among antenna element groups (i.e., θ_(p)) were used as one of the codebook design factors. The disclosed scheme targets multi-panel transmission with extension of the same design foundation over multiple panels, instead of multiple antenna groups of one panel, where inter-panel co-phasing (i.e. φ_(p)) is used as one of the precoder matrix design multiplexing factors. A simple codebook design of such a scheme for a one-to-eight layer transmission under Mode 1 with two panels is defined in Equations (13)-(20) as shown below. In Equations (14)-(21), each beam can be used to provide up to rank-4 transmission.

$\begin{matrix} {W_{l,m,p,n}^{(1)} = {\frac{1}{\sqrt{P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} \\ {\varphi_{p}v_{l,m}} \\ {\varphi_{n}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (14) \end{matrix}$ $\begin{matrix} {W_{l,m,p,n}^{(2)} = {\frac{1}{\sqrt{2P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} \\ {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (15) \end{matrix}$ $\begin{matrix} {W_{l,m,p,n}^{(3)} = {\frac{1}{\sqrt{3P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} \\ {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l,m}} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (16) \end{matrix}$ $\begin{matrix} {W_{l,m,p,n}^{(4)} = {\frac{1}{\sqrt{4P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} \\ {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (17) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(5)} = {\frac{1}{\sqrt{5P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} \end{bmatrix}}} & (18) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(6)} = {\frac{1}{\sqrt{6P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} \end{bmatrix}}} & (19) \end{matrix}$ $\begin{matrix} {{W_{l,l^{\prime},m,m^{\prime},p,n}^{(7)} = \frac{1}{\sqrt{7P_{{CSI} - {RS}}}}}\text{ }\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} \end{bmatrix}} & (20) \end{matrix}$ $\begin{matrix} {{W_{l,l^{\prime},m,m^{\prime},p,n}^{(8)} = \frac{1}{\sqrt{8P_{{CSI} - {RS}}}}}\text{ }\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} \end{bmatrix}} & (21) \end{matrix}$

In the scheme defined in Equations (14)-(21), the precoder matrix design priority is transmission over multi-panel, cross polarization and multi-beam. This design may be inefficient for cross polar antenna panels where cross polarization transmission is prioritized over multi-panel transmission. Hence, another design approach for the disclosed scheme is to change the precoder matrix design priority rule to cross polarization, multi-panel and multi-beam transmissions. For example, the codebook design for a one-to-eight layer transmission under Mode 1 with two panels is defined in Equations (22)-(29) as shown below. Similar to Equations (14)-(21), each beam in Equations (22)-(29) can be used to provide up to rank-4 transmission.

$\begin{matrix} {W_{l,m,p,n}^{(1)} = {\frac{1}{\sqrt{P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} \\ {\varphi_{n}v_{l,m}} \\ {\varphi_{p}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (22) \end{matrix}$ $\begin{matrix} {W_{l,m,p,n}^{(2)} = {\frac{1}{\sqrt{2P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} \\ {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (23) \end{matrix}$ $\begin{matrix} {W_{l,m,p,n}^{(3)} = {\frac{1}{\sqrt{3P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} \\ {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l,m}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (24) \end{matrix}$ $\begin{matrix} {W_{l,m,p,n}^{(4)} = {\frac{1}{\sqrt{4P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} \\ {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (25) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(5)} = {\frac{1}{\sqrt{5P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} \end{bmatrix}}} & (26) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(6)} = {\frac{1}{\sqrt{6P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} \end{bmatrix}}} & (27) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(7)} = {\frac{1}{\sqrt{7P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} \end{bmatrix}}} & (28) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(8)} = {\frac{1}{\sqrt{8P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} \end{bmatrix}}} & (29) \end{matrix}$

In the scheme defined in Equations (22)-(29), the precoder matrix design priority is cross polarization, multi-panel and multi-beam transmissions. However, for consistency with the current specification, the prioritization rule of this codebook design scheme is further modified to first perform cross polarization followed by multi-beam transmission with up to two beams as in the current specification for the Type I multi-panel codebook, and then multi-panel transmissions. Thus, the codebook design for a one-to-eight layer transmission under Mode 1 for a two panel scenario is defined below in Equations (30)-(37) where the codebook for one to four layer transmission is identical to the current specification.

$\begin{matrix} {W_{l,m,p,n}^{(1)} = {\frac{1}{\sqrt{P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} \\ {\varphi_{n}v_{l,m}} \\ {\varphi_{p}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (30) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(2)} = {\frac{1}{\sqrt{2P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} \end{bmatrix}}} & (31) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(3)} = {\frac{1}{\sqrt{3P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l,m} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l,m}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (32) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(4)} = {\frac{1}{\sqrt{4P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} \end{bmatrix}}} & (33) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(5)} = {\frac{1}{\sqrt{5P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l,m} \\ {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} & {\varphi_{n}v_{l,m}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (34) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(6)} = {\frac{1}{\sqrt{6P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l,m} & v_{l,m} \\ {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (35) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(7)} = {\frac{1}{\sqrt{7P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l,m} & v_{l,m} & v_{l,m} \\ {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l,m}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (36) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(8)} = {\frac{1}{\sqrt{8P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l,m} & v_{l,m} & v_{l,m} & v_{l,m} \\ {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} & {\varphi_{n}v_{l,m}} & {{- \varphi_{n}}v_{l,m}} & {\varphi_{n}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l,m}} \\ {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l,m}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l,m}} & {{- \varphi_{p}}v_{l,m}} & {{- \varphi_{p}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{p}}v_{l,m}} \\ {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} & {{- \varphi_{n}}\varphi_{p}v_{l,m}} & {\varphi_{n}\varphi_{p}v_{l,m}} \end{bmatrix}}} & (37) \end{matrix}$

It is assumed all panels are identical in terms of the number of antennas, spacing, and inter-polarization co-phasing. Since a constant inter-polarization co-phasing per panel may be an unrealistic assumption, Mode 2 reporting provides more accurate and higher resolution information on the combination of inter-panel and inter-polarization co-phasing. With the introduction of MIMO precoding over panels, the Mode 2 codebook for a rank-R transmission is modified as shown below in Equation (38).

$\begin{matrix} {W_{l,l^{\prime},{\ldots l^{\prime\prime\prime\prime}},m,m^{\prime},\ldots,m^{\prime\prime\prime\prime},p,n}^{(8)} = \left\{ \begin{matrix} {{\frac{1}{\sqrt{{RP}_{{CSI} - {RS}}}}\begin{bmatrix} \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} & & 0 \\  & \ddots & \\ 0 & & \begin{bmatrix} v_{l^{\prime\prime\prime\prime},m^{\prime\prime\prime\prime}} & 0 \\ 0 & v_{l^{\prime\prime\prime\prime},m^{\prime\prime\prime\prime}} \end{bmatrix} \end{bmatrix}}C_{MIMO}} & {{{if}{{mod}\left( {R,4} \right)}} = 0} \\ {{\frac{1}{\sqrt{{RP}_{{CSI} - {RS}}}}\begin{bmatrix} \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} & & 0 \\  & \ddots & \\ 0 & & \begin{bmatrix} \begin{bmatrix} v_{l^{\prime\prime\prime\prime},m^{\prime\prime\prime\prime}} & 0 \\ 0 & v_{l^{\prime\prime\prime\prime},m^{\prime\prime\prime\prime}} \end{bmatrix} & 0 \\ 0 & v_{l^{\prime\prime\prime\prime},m^{\prime\prime\prime\prime}} \end{bmatrix} \end{bmatrix}}C_{MIMO}} & {{{if}{mod}\left( {R,4} \right)} = 3} \\ {{\frac{1}{\sqrt{{RP}_{{CSI} - {RS}}}}\begin{bmatrix} \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} & & 0 \\  & \ddots & \\ 0 & & \begin{bmatrix} v_{l^{\prime\prime\prime\prime},m^{\prime\prime\prime\prime}} & 0 \\ 0 & v_{l^{\prime\prime\prime\prime},m^{\prime\prime\prime\prime}} \end{bmatrix} \end{bmatrix}}C_{MIMO}} & {{{if}{mod}\left( {R,4} \right)} = 2} \\ {{\frac{1}{\sqrt{{RP}_{{CSI} - {RS}}}}\begin{bmatrix} \begin{bmatrix} v_{l,m} & 0 \\ 0 & v_{l,m} \end{bmatrix} & & 0 \\  & \ddots & \\ 0 & & \left\lbrack v_{l^{\prime\prime\prime\prime},m^{\prime\prime\prime\prime}} \right\rbrack \end{bmatrix}}C_{MIMO}} & {{{if}{mod}\left( {R,4} \right)} = 1} \end{matrix} \right.} & (38) \end{matrix}$

In Equation (38), C_(MIMO) is a MIMO precoding matrix over both panel and polarization that is defined in Equation (39) as follows.

$\begin{matrix} {C_{MIMO} = \begin{bmatrix} \begin{bmatrix} 1 & 1 & 1 & 1 \\ \varphi_{n_{0}} & {- \varphi_{n_{0}}} & \varphi_{n_{0}} & {- \varphi_{n_{0}}} \\ {a_{p_{1}}b_{n_{1}}} & {a_{p_{1}}b_{n_{1}}} & {{- a_{p_{1}}}b_{n_{1}}} & {{- a_{p_{1}}}b_{n_{1}}} \\ {a_{p_{2}}b_{n_{2}}} & {{- a_{p_{2}}}b_{n_{2}}} & {{- a_{p_{2}}}b_{n_{2}}} & {a_{p_{2}}b_{n_{2}}} \end{bmatrix} \\  \vdots \\ \begin{bmatrix} 1 & 1 & 1 & 1 \\ \varphi_{n_{K - 2}} & {- \varphi_{n_{K - 2}}} & \varphi_{n_{K - 2}} & {- \varphi_{n_{K - 2}}} \\ {a_{p_{{2K} - 3}}b_{n_{{2K} - 3}}} & {a_{p_{{2K} - 3}}b_{n_{{2K} - 3}}} & {{- a_{p_{{2K} - 3}}}b_{n_{{2K} - 3}}} & {{- a_{p_{{2K} - 3}}}b_{n_{{2K} - 3}}} \\ {a_{p_{{2K} - 2}}b_{n_{{2K} - 2}}} & {{- a_{p_{{2K} - 2}}}b_{n_{{2K} - 2}}} & {{- a_{p_{{2K} - 2}}}b_{n_{{2K} - 2}}} & {a_{p_{{2K} - 2}}b_{n_{{2K} - 2}}} \end{bmatrix} \end{bmatrix}} & (39) \end{matrix}$

In Equation (39), a_(p) _(k) k=1, . . . , 2(K−1) are wide-band combined inter-polarization and inter-panel co-phasing reported at stage 1 of Mode 2 for K panels (i.e. two phase shifts of a_(p) _(2k−3) and a_(p) _(2k−2) for k^(th) panel) and φ_(n) _(k) k=0, . . . , K−2 and b_(n) _(k) k=1, . . . , 2(K−1) are sub-band combined inter-polarization and inter-panel co-phasing reported at stage 2 of Mode 2 for K panels (three phase shifts of φ_(n) _(k−2) , b_(n) _(2k−3) , b_(n) _(2k−2) for k^(th) panel). In the current specification, max(K)=2 for Mode 2.

In the above scheme, the priority of precoder matrix design is cross polarization, multi-panel transmission, and multi-beam transmissions. As previously discussed, the codebook design scheme priority can be modified to first perform cross polarization, followed by multi-beam transmission with up to two beams as in the current specification for the Type I multi-panel codebook, and then multi-panel transmissions. The codebook design for a one-to-eight layer transmission under Mode 2 with two panels and with spatial multiplexing prioritization consistent with the current specification is defined in Equations (40)-(47) as follows.

$\begin{matrix} {W_{l,m,p,n}^{(1)} = {\frac{1}{\sqrt{P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} \\ {\varphi_{n_{0}}v_{l,m}} \\ {a_{p_{1}}b_{n_{1}}v_{l,m}} \\ {a_{p_{2}}b_{n_{2}}v_{l,m}} \end{bmatrix}}} & (40) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(2)} = {\frac{1}{\sqrt{2P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{n_{0}}v_{l,m}} & {\varphi_{n_{0}}v_{l^{\prime},m^{\prime}}} \\ {a_{p_{1}}b_{n_{1}}v_{l,m}} & {a_{p_{1}}b_{n_{1}}v_{l^{\prime},m^{\prime}}} \\ {a_{p_{2}}b_{n_{2}}v_{l,m}} & {a_{p_{2}}b_{n_{2}}v_{l^{\prime},m^{\prime}}} \end{bmatrix}}} & (41) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(3)} = {\frac{1}{\sqrt{3P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l,m} \\ {\varphi_{n_{0}}v_{l,m}} & {\varphi_{n_{0}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n_{0}}}v_{l,m}} \\ {a_{p_{1}}b_{n_{1}}v_{l,m}} & {a_{p_{1}}b_{n_{1}}v_{l^{\prime},m^{\prime}}} & {a_{p_{1}}b_{n_{1}}v_{l,m}} \\ {a_{p_{2}}b_{n_{2}}v_{l,m}} & {a_{p_{2}}b_{n_{2}}v_{l^{\prime},m^{\prime}}} & {{- a_{p_{2}}}b_{n_{2}}v_{l,m}} \end{bmatrix}}} & (42) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(4)} = {\frac{1}{\sqrt{4P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l,m} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{n_{0}}v_{l,m}} & {\varphi_{n_{0}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n_{0}}}v_{l,m}} & {\varphi_{n_{0}}v_{l^{\prime},m^{\prime}}} \\ {a_{p_{1}}b_{n_{1}}v_{l,m}} & {a_{p_{1}}b_{n_{1}}v_{l^{\prime},m^{\prime}}} & {a_{p_{1}}b_{n_{1}}v_{l,m}} & {{- a_{p_{1}}}b_{n_{1}}v_{l^{\prime},m^{\prime}}} \\ {a_{p_{2}}b_{n_{2}}v_{l,m}} & {a_{p_{2}}b_{n_{2}}v_{l^{\prime},m^{\prime}}} & {{- a_{p_{2}}}b_{n_{2}}v_{l,m}} & {{- a_{p_{2}}}b_{n_{2}}v_{l^{\prime},m^{\prime}}} \end{bmatrix}}} & (43) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(5)} = {\frac{1}{\sqrt{5P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l,m} \\ {\varphi_{n_{0}}v_{l,m}} & {{- \varphi_{n_{0}}}v_{l,m}} & {\varphi_{n_{0}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} & {\varphi_{n_{0}}v_{l,m}} \\ {a_{p_{1}}b_{n_{1}}v_{l,m}} & {a_{p_{1}}b_{n_{1}}v_{l,m}} & {a_{p_{1}}b_{n_{1}}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- a_{p_{1}}}b_{n_{1}}v_{l,m}} \\ {a_{p_{2}}b_{n_{2}}v_{l,m}} & {{- a_{p_{2}}}b_{n_{2}}v_{l,m}} & {a_{p_{2}}b_{n_{2}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- a_{p_{2}}}b_{n_{2}}v_{l,m}} \end{bmatrix}}} & (44) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(6)} = {\frac{1}{\sqrt{6P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l,m} & v_{l,m} \\ {\varphi_{n_{0}}v_{l,m}} & {{- \varphi_{n_{0}}}v_{l,m}} & {\varphi_{n_{0}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} & {\varphi_{n_{0}}v_{l,m}} & {{- \varphi_{n_{0}}}v_{l,m}} \\ {a_{p_{1}}b_{n_{1}}v_{l,m}} & {a_{p_{1}}b_{n_{1}}v_{l,m}} & {a_{p_{1}}b_{n_{1}}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- a_{p_{1}}}b_{n_{1}}v_{l,m}} & {{- a_{p_{1}}}b_{n_{1}}v_{l,m}} \\ {a_{p_{2}}b_{n_{2}}v_{l,m}} & {{- a_{p_{2}}}b_{n_{2}}v_{l,m}} & {a_{p_{2}}b_{n_{2}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- a_{p_{2}}}b_{n_{2}}v_{l,m}} & {a_{p_{2}}b_{n_{2}}v_{l,m}} \end{bmatrix}}} & (45) \end{matrix}$ $\begin{matrix} {W_{l,l^{\prime},m,m^{\prime},p,n}^{(7)} = {\frac{1}{\sqrt{7P_{{CSI} - {RS}}}}\begin{bmatrix} v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} & v_{l^{\prime},m^{\prime}} & v_{l,m} & v_{l,m} & v_{l^{\prime},m^{\prime}} \\ {\varphi_{n_{0}}v_{l,m}} & {{- \varphi_{n_{0}}}v_{l,m}} & {\varphi_{n_{0}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}v_{l^{\prime},m^{\prime}}} & {\varphi_{n_{0}}v_{l,m}} & {{- \varphi_{n_{0}}}v_{l,m}} & {\varphi_{n_{0}}v_{l^{\prime},m^{\prime}}} \\ {a_{p_{1}}b_{n_{1}}v_{l,m}} & {a_{p_{1}}b_{n_{1}}v_{l,m}} & {a_{p_{1}}b_{n_{1}}v_{l^{\prime},m^{\prime}}} & {\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- a_{p_{1}}}b_{n_{1}}v_{l,m}} & {{- a_{p_{1}}}b_{n_{1}}v_{l,m}} & {{- a_{p_{1}}}b_{n_{1}}v_{l^{\prime},m^{\prime}}} \\ {a_{p_{2}}b_{n_{2}}v_{l,m}} & {{- a_{p_{2}}}b_{n_{2}}v_{l,m}} & {a_{p_{2}}b_{n_{2}}v_{l^{\prime},m^{\prime}}} & {{- \varphi_{n}}\varphi_{p}v_{l^{\prime},m^{\prime}}} & {{- a_{p_{2}}}b_{n_{2}}v_{l,m}} & {a_{p_{2}}b_{n_{2}}v_{l,m}} & {{- a_{p_{2}}}b_{n_{2}}v_{l^{\prime},m^{\prime}}} \end{bmatrix}}} & (46) \end{matrix}$ W l , l ′ , m , m ′ , p , n ( 8 ) = 1 8 ⁢ P CSI - RS [ v l , m v l , m v l ′ , m ′ v l ′ , m ′ v l , m v l , m v l , m v l ′ , m ′ φ n 0 ⁢ v l , m - φ n 0 ⁢ v l , m φ n 0 ⁢ v l ′ , m ′ - φ n ⁢ v l ′ , m ′ φ n 0 ⁢ v l , m - φ n 0 ⁢ v l , m φ n 0 ⁢ v l , m n 0 v l ′ , m ′ a p 1 ⁢ b n 1 ⁢ v l , m a p 1 ⁢ b n 1 ⁢ v l , m a p 1 ⁢ b n 1 ⁢ v l ′ , m ′ φ p ⁢ v l ′ , m ′ - a p 1 ⁢ b n 1 ⁢ v l , m - a p 1 ⁢ b n 1 ⁢ v l , m - a p 1 ⁢ b n 1 ⁢ v l , m - a p 1 ⁢ b n 1 ⁢ v l ′ , m ′ a p 2 ⁢ b n 2 ⁢ v l , m - a p 2 ⁢ b n 2 ⁢ v l , m a p 2 ⁢ b n 2 ⁢ v l ′ , m ′ - φ n ⁢ φ p ⁢ v l ′ , m ′ - a p 2 ⁢ b n 2 ⁢ v l , m a p 2 ⁢ b n 2 ⁢ v l , m - a p 2 ⁢ b n 2 ⁢ v l , m a p 2 ⁢ b n 2 ⁢ v l ′ , m ′ ] ( 47 )

Type II Codebook Refinement for CJT mTRP Targeting FDD

The Type II codebook design targets multi-use MIMO scenarios with support of up to two layers. The Type II codebook provides more accurate channel state information compared to the Type I codebook but increases the signaling overhead for PMI reporting. In the Type II codebook design, a set of beams and a set of amplitude and phase shift coefficients are used to generate a weighted combination of beams. The number of beams L that are combined are RRC configured to the UE. Antenna configuration for the Type II codebook design is defined by N₁ as the number of cross polar antenna element columns and N₂ as the number of cross polar antenna element rows. The number of candidate beam groups to be selected is N₁N₂ groups of beams.

The Type II codebook design provides two solutions of single panel and port selection designs where, for both solutions, the PMI reporting has dual stages of reporting. In both Type II codebook designs, the UE reports at stage 1 the location of one beam within the group (i.e., a fixed location across group) as well as a set of L beam groups. At stage 1, a set of beam groups is selected with the assumption that the same beams are used for different polarization and layers. The strongest beam is then identified from all beam groups across both polarizations and layers and wideband amplitude coefficients are applied to the beams accordingly. The beams associated with each polarization and layer are considered to be independent. The UE reports phase shift of different beams relative to the strongest beam as well as sub-band amplitude coefficients at stage 2 reporting.

The i parameters are used by the UE to report channel state information to a gNB, where i_(1,1) indicates one specific location within a beam group that is identified with q₁, q₂ parameters, i_(1,2) indicates L beam groups selection among N₁N₂ candidate beam groups (i.e. i_(1,2) indicates one of the

$\begin{pmatrix} {N_{1}N_{2}} \\ L \end{pmatrix}$

possible cases) presented by n₁ ^((i)), n₂ ^((i)) parameters, i_(1,3,l) is the strongest coefficient (based on having the largest amplitude coefficient or strongest power) on layer l, i_(1,4,l) are wideband amplitude coefficients for layer l, i_(2,1,l) are phase coefficients for layer l that takes values from QPSK or 8PSK, i_(2,2,l) is sub-band amplitude coefficients for layer l.

The Type II port selection codebook solution assumes a gNB already has some knowledge of a propagation channel, either through channel reciprocity or a beam management procedure. Alternatively, the Type II port selection codebook can be seen as a two-step hybrid process, where the first step provides coarse channel state information to the gNB and the second step is similar to the Type II single panel codebook.

Since the gNB has some coarse knowledge of propagation channel, the Type II port selection codebook design is based on a set of actual beamformed CSI-RS transmissions and does not rely on a hypothetical beam position using oversampling factors as in the Type II single panel codebook. In the Type II port selection codebook solution, the first stage of PMI reporting includes reporting of a first beam selection and other L−1 beams are identified to be adjacent to the first selected beam. The first beam is selected among the over-sampled candidate beams with sampling factor d where port selection sampling (i.e., d) is RRC configured to the UE to specify the spacing between candidate beams for first beam selection. The remainder of the PMI reporting procedure is the same as the Type II single panel codebook.

The i parameters are used by the UE to report channel state information to the gNB, where i_(1,1) indicates one specific location of the first selected beam and the other L−1 beams are located at i_(1,1)d+{1, . . . , L−1}), i_(1,3,l) is the strongest coefficient on layer l, i_(1,4,l) are wideband amplitude coefficients for layer l, i_(2,1,l) is the phase coefficient for layer l that takes values from QPSK or 8PSK, and i_(2,2,l) is the sub-band amplitude coefficient for layer l.

The generation of the precoding matrix for the Type II codebook is based on a linear combination of a set of L beams that are combined using a set of relative amplitude and phase shift coefficients per polarization and per layer. The Type II single panel and port selection codebooks are defined in Equations (48)-(50) as shown below in the current specification for the Type II single panel codebook as in Tables 5.2.2.2.3-5 in TS 38.214.

$\begin{matrix} {W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{(1)} = W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1}} & (48) \end{matrix}$ $\begin{matrix} {W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1} = {\frac{1}{\sqrt{2}}\begin{bmatrix} W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1} & W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,2}}^{1} \end{bmatrix}}} & (49) \end{matrix}$ with $\begin{matrix}  & (50) \end{matrix}$ $W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,l}}^{l} = {\frac{1}{\sqrt{N_{1}N_{2}{\sum_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)},p_{l,i}^{(2)}} \right)^{2}}}}\begin{bmatrix} \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i + L}}}} \end{bmatrix} \\  \vdots \\ {\theta_{p_{K - 1}}\begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i + L}}}} \end{bmatrix}} \end{bmatrix}}$ l = 1, 2

where v_(m) ₁ _((i)) _(,m) ₂ _((i)) is the 2D DFT virtualization coefficient for i^(th) beam with m₁ ^((i))=O₁n₁ ^((i))+q₁ and m₂ ^((i))=O₂n₂ ^((i))+q₂, q₁, q₂ are indicated by i_(1,1) and n₁ ^((i)), n₂ ^((i)) are indicated by i_(1,2), p_(l,i) ⁽¹⁾, p_(l,i+L) ⁽¹⁾ and p_(l,i) ⁽²⁾, p_(l,i+L) ⁽²⁾ are wide-band and sub-band amplitude coefficients for i^(th) beam two polarizations, φ_(l,i), φ_(l,i+L) are phase shift coefficients for i^(th) beam two polarizations. Equations (51)-(53) below are defined for the Type II port selection codebook as in Table 5.2.2.2.4-1 in TS 38.214.

$\begin{matrix} {W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{(1)} = W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1}} & (51) \end{matrix}$ $\begin{matrix} {W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,2}}^{(2)} = {\frac{1}{\sqrt{2}}\begin{bmatrix} W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1} & W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,2}}^{2} \end{bmatrix}}} & (52) \end{matrix}$ with $\begin{matrix}  & (53) \end{matrix}$ $W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},c_{l}}^{l} = {\frac{1}{\sqrt{\sum_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)},p_{l,i}^{(2)}} \right)^{2}}}\left\lbrack \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i + L}}}} \end{bmatrix} \right\rbrack}$ l = 1, 2

Where v_(i) _(1,1) _(d+i) is the 2D DFT virtualization coefficient for the i^(th) beam, p_(l,i) ⁽¹⁾, p_(l,i+L) ⁽¹⁾ and p_(l,i) ⁽²⁾, p_(l,i+L) ⁽²⁾ are wide-band and sub-band amplitude coefficients for the i^(th) beam two polarizations, and φ_(l,i), φ_(l,i+L) are phase shift coefficients for the i^(th) beam two polarizations.

A new design for the multi-panel scenario is now disclosed for the Type II codebook to address the CJT scenario. In the current specification, Type II codebook design focuses on providing more detailed channel state information for a single panel scenario in multi-user MIMO deployment and is based on a weighted combination of a set of beams. The relative amplitude and phase shift coefficient for each beam are specified with respect to the strongest beam.

Starting with the Type II single panel codebook and expanding the design for multi-panel to address the CJT scenario, one approach is to introduce an inter-panel co-phasing concept similar to the Type I multi-panel codebook. In such a scheme, the Type II codebook design is enhanced with the assumption that all panels are similar in terms of physical configuration (e.g., the panel shape, antenna elements structure, single or cross polar antenna elements, and arrangement, number, and type of the antenna elements) and different panels are quasi co-located and experience similar long term channel characteristics involving wideband PMI information such as beam selection. Similar to the Type I codebook, each panel has N₁N₂ antenna ports. Assuming multiple panels are similar and share the same beams, with the application of inter-panel co-phasing across different panels (i.e., group of N₁N₂ ports), coherent joint precoding is achieved across multiple panels for a CJT multi-TRP scenario. In this scheme, a set of L beam groups are first selected to be shared across polarizations, layers and panels. Next, the strongest beam is identified per layer across both polarizations where a set of amplitude and phase shift coefficients are applied to beams accordingly. That is, the beams associated with each polarization and layer are considered to be independent but similar across different panels. PMI reporting is accomplished by the UE reporting i_(1,1) and i_(1,2) to indicate L beams/beam groups, i_(1,3,l) to indicate the strongest coefficient on layer l, i_(1,4,l) to indicate wideband amplitude coefficients for layer l, i_(2,1,l) to indicate the phase coefficient for layer l, i_(2,2,l) to indicate the sub-band amplitude coefficient for layer l, and the i_(2,3,k) parameter is introduced to indicate inter-panel co-phasing for panel k with respect to a first, reference, or pre-determined panel. Thus, the Type II multi-panel codebook for a rank R transmission is defined in Equation (54) as follows.

$\begin{matrix} {W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,l}}^{(R)} = {\frac{1}{\sqrt{R}}\left\lbrack {W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1}\cdots W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{R}} \right\rbrack}} & (54) \end{matrix}$

In Equation (54), each column of W_(q) ₁ _(,q) ₂ _(,n) ₁ _(,n) ₂ _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,R) ^((R)) matrix indicates the precoding coefficients for each layer of transmission. The column l corresponding to the precoding coefficient of layer l is defined in Equation (55) as follows.

$\begin{matrix}  & (55) \end{matrix}$ $W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,l}}^{l} = {\frac{1}{\sqrt{N_{1}N_{2}{\sum_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)},p_{l,i}^{(2)}} \right)^{2}}}}\begin{bmatrix} \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i + L}}}} \end{bmatrix} \\  \vdots \\ {\theta_{p_{K - 1}}\begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i + L}}}} \end{bmatrix}} \end{bmatrix}}$ l = 1, …, R

where the k^(th) matrix block in Equation (55) for W_(q) ₁ _(,q) ₂ _(,n) ₁ _(,n) ₂ _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,l) ^(l), i.e.,

${\theta_{p_{k - 1}}\begin{bmatrix} {\sum_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\ {\sum_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i + L}}}} \end{bmatrix}},$

corresponds to the k^(th) panel where θ_(p) _(k−1) is the inter-panel co-phasing of k^(th) panel with respect to the first panel in order to achieve coherent joint precoding across panels (note that θ_(p) _(o) =1 and is omitted from the Equations for conciseness). The Σ_(i=0) ^(L−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i) ⁽¹⁾p_(l,i) ⁽²⁾φ_(l,i) is the beamforming virtualization coefficients of N₁N₂ ports for first polarized antenna elements and Σ_(i=0) ^(L−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i+L) ⁽¹⁾p_(l,i+L) ⁽²⁾φ_(l,i+L) is the beamforming virtualization coefficients of N₁N₂ ports for second polarized antenna elements in all panels. The beamforming virtualization coefficients are unchanged across all panels as different panels share the same beam per polarization for each layer. The v_(m) ₁ _((i)) _(,m) ₂ _((i)) is the 2D DFT virtualization coefficient for the i^(th) beam, p_(l,i) ⁽¹⁾, p_(l,i+L) ⁽¹⁾ and p_(l,i) ⁽²⁾, p_(l,i+L) ⁽²⁾ are wide-band and sub-band amplitude coefficients for the i^(th) beam two polarizations with respect to the strongest beam, and φ_(l,i), φ_(l,i+L) are phase shift coefficients for the i^(th) beam two polarizations with respect to the strongest beam. Hence, K blocks in W_(q) ₁ _(,q) ₂ _(,n) ₁ _(,n) ₂ _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,l) ^(l) provide beamforming virtualization coefficients over K groups of N₁N₂ ports that are coherently combined to provide a joint precoder matrix for a multi panel scenario.

Similarly, for the Type II port selection, the enhanced multi-panel codebook design is defined in Equation (56) as follows.

$\begin{matrix} {W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{(R)} = {\frac{1}{\sqrt{R}}\left\lbrack {W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1}\cdots W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{R}} \right\rbrack}} & (56) \end{matrix}$

where precoding coefficients of layer l (i.e., column l of W_(i) _(1,1) _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,R) ^((R))) is defined in Equation (57) as follows.

$\begin{matrix}  & (57) \end{matrix}$ $W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,i}}^{l} = {\frac{1}{\sqrt{\sum_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)},p_{l,i}^{(2)}} \right)^{2}}}\begin{bmatrix} \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i + L}}}} \end{bmatrix} \\  \vdots \\ {\theta_{p_{K - 1}}\begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i + L}}}} \end{bmatrix}} \end{bmatrix}}$ l = 1, …, R

where the k^(th) matrix block in Equation (57) for W_(i) _(1,1) _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,l) ^(l), i.e.,

${\theta_{p_{K - 1}}\begin{bmatrix} {\sum_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\ {\sum_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,{i + L}}}} \end{bmatrix}},$

corresponds to the k^(th) panel where θ_(p) _(k−1) is the inter-panel co-phasing of the k^(th) panel with respect to the first panel in order to achieve coherent joint precoding across panels. The Σ_(i=0) ^(L−1)v_(i) _(1,1) _(d+i)p_(l,i) ⁽¹⁾p_(l,i) ⁽²⁾φ_(l,i) is the beamforming virtualization coefficients of N₁N₂ ports for first polarized antenna elements and Σ_(i=0) ^(L−1)v_(i) _(1,1) _(d+i)p_(l,i) ⁽¹⁾p_(l,i) ⁽²⁾φ_(l,i+L) is the beamforming virtualization coefficients of N₁N₂ ports for second polarized antenna elements in all panels as different panels share the same beam per polarization for each layer. The coefficient v_(i) _(1,1) _(d+i) is the 2D DFT virtualization coefficient for i^(th) beam, p_(l,i) ⁽¹⁾, p_(l,i+L) ⁽¹⁾ and p_(l,i) ⁽²⁾, p_(l,i+L) ⁽²⁾ are wide-band and sub-band amplitude coefficients for the i^(th) beam two polarizations with respect to the strongest beam, and φ_(l,i), φ_(l,i+L) are phase shift coefficients for the i^(th) beam two polarizations with respect to the strongest beam. Hence, K blocks in W_(i) _(1,1) _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,l) ^(l) provide beamforming virtualization coefficients over K groups of N₁N₂ ports that are coherently combined to provide a joint precoder matrix for a multi panel scenario.

In the above scheme, all panels are similar in terms of the number of antennas and spacing, and are quasi co-located in terms of beams selection and employment of amplitude and phase shift coefficients for generating the combined beam. As previously discussed, however, this assumption may be unsuitable for distributed MIMO scenario or FR2 applications. To address this issue, the disclosure enables different amplitude and phase shift coefficients per panel for generating the linearly combined beam. That is, the beam per layer, per polarization and per panel is an independent linear combination of L selected group of beams in which a set of L beam groups is first selected to be shared across polarizations, layers and panels. The selection of those initial L beams can be performed through transmission across all panels or from a specific panel. The strongest beam is then identified per layer, across both polarizations and all panels where a set of amplitude and phase shift coefficients are applied to beams accordingly with respect to the identified strongest beam. PMI reporting is accomplished by the UE reporting i_(1,1) and i_(1,2) to indicate L beams/beam groups, i_(1,3,l) to indicate the strongest coefficient on layer l, i_(1,4,l) to indicate wideband amplitude coefficients for layer l), i_(1,2,l) to indicate the phase coefficient for layer l, and i_(2,2,l) to indicate the sub-band amplitude coefficient for layer l. The i parameters i_(1,4,l), i_(2,1,l) and i_(2,2,l) in this scheme take 2KL values where K is the number of panels. For each layer of transmission, there is a set of L coefficients per polarization and per panel for each of the i parameters. Alternatively, the definitions of i_(1,4,l), i_(2,1,l) and i_(2,2,l) parameters are modified to i_(1,4,l,k), i_(2,1,l,k) and i_(2,2,l,k) to indicate amplitude and phase shift coefficients for layer l on panel k where each takes 2L values as in the current specification for two polarizations. For consistency with the current specification, the following Equations (58) and (59) are derived to define the Type II multi-panel codebook.

$\begin{matrix} {W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{(R)} = {\frac{1}{\sqrt{R}}\left\lbrack {W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1}\cdots W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{R}} \right\rbrack}} & (58) \end{matrix}$

where each column of W_(q) ₁ _(,q) ₂ _(,n) ₁ _(,n) ₂ _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,R) ^((R)) matrix indicates the precoding coefficients for each layer of transmission. The column 1 corresponding to precoding coefficient of layer l is defined in Equation (59) as follows.

$\begin{matrix} {{W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,l}}^{l} = \frac{1}{\sqrt{N_{1}N_{2}{\sum}_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)}p_{l,i}^{(2)}} \right)^{2}}}}\text{ }{{{\begin{bmatrix} \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i + L}}}} \end{bmatrix} \\  \vdots \\ \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + {L({{2K} - 2})}}}^{(1)}p_{l,{i + {L({{2K} - 2})}}}^{(2)}\varphi_{l,{i + {L({{2K} - 2})}}}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + {L({{2K} - 1})}}}^{(1)}p_{l,{i + {L({{2K} - 1})}}}^{(2)}\varphi_{l,{i + {L({{2K} - 1})}}}}} \end{bmatrix} \end{bmatrix}l} = 1},\ldots,R}} & (59) \end{matrix}$ wherethek^(th)matrixblockinEquation(59)forW_(q₁, q₂, n₁, n₂, p_(l)⁽¹⁾, p_(l)⁽²⁾, i_(2, 1, l),)^(l) ${i.e.\begin{bmatrix} {{\sum}_{i = 0}^{L - 1}v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + {L({{2K} - 2})}}}^{(1)}p_{l,{i + {L({{2K} - 2})}}}^{(2)}\varphi_{l,{i + {L({{2K} - 2})}}}} \\ {{\sum}_{i = 0}^{L - 1}v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + {L({{2K} - 1})}}}^{(1)}p_{l,{i + {L({{2K} - 1})}}}^{(2)}\varphi_{l,{i + {L({{2K} - 1})}}}} \end{bmatrix}},$

corresponds to the k^(th) panel where p_(l,i+L(2k−2)) ⁽¹⁾ and p_(l,i+L(2k−2)) ⁽²⁾ k=1, . . . , K are wide-band and sub-band amplitude coefficients for the i^(th) beam of the k^(th) panel for first polarized antenna elements, p_(l,i+L(2k−1)) ⁽¹⁾ and p_(l,i+L(2k−1)) ⁽²⁾ k=1, . . . , K are wide-band and sub-band amplitude coefficients for the i^(th) beam of the k^(th) panel for second polarized antenna elements, φ_(l,i+L(2k−2)), φ_(l,i+L(2k−1)) k=1, . . . , K are phase shift coefficients for the i^(th) beam of the k^(th) panel for first and second polarized antenna elements, respectively, and v_(m) ₁ _((i)) _(,m) ₂ _((i)) is the 2D DFT virtualization coefficient for the i^(th) beam. The Σ_(i=0) ^(L−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i+L(2k−2)) ⁽¹⁾p_(l,i+L(2k−2)) ⁽²⁾φ_(l,i+L(2k−2)) are the beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for the first polarized antenna elements and Σ_(i=0) ^(L−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i+L(2k−1)) ⁽¹⁾p_(l,i+L(2k−1)) ⁽²⁾φ_(l,i+L(2k−1)) are the beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for the second polarized antenna elements. Hence, for each layer of transmission, the L selected beams are combined with different sets of amplitude and phase shift coefficients per polarization in each panel.

Similarly, for the Type II port selection, the enhanced multi-panel codebook design is defined in Equations (60) and (61) as follows.

$\begin{matrix} {W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{(R)} = {\frac{1}{\sqrt{R}}\left\lbrack \begin{matrix} \begin{matrix} W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1} & \ldots \end{matrix} & \left. W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{R} \right\rbrack \end{matrix} \right.}} & (60) \end{matrix}$ where $\begin{matrix} {{W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,l}}^{l} = \frac{1}{\sqrt{{\sum}_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)}p_{l,i}^{(2)}} \right)^{2}}}}\text{ }{{{\begin{bmatrix} \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{(1)}p_{l,i}^{(2)}\varphi_{l,i}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + L}}^{(1)}p_{l,{i + L}}^{(2)}\varphi_{l,{i + L}}}} \end{bmatrix} \\  \vdots \\ \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + {L({{2K} - 2})}}}^{(1)}p_{l,{i + {L({{2K} - 2})}}}^{(2)}\varphi_{l,{i + {L({{2K} - 2})}}}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + {L({{2K} - 1})}}}^{(1)}p_{l,{i + {L({{2K} - 1})}}}^{(2)}\varphi_{l,{i + {L({{2K} - 1})}}}}} \end{bmatrix} \end{bmatrix}l} = 1},\ldots,R}} & (61) \end{matrix}$

where the k^(th) matrix block in Equation (61) for W_(i) _(1,1) _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,l) ^(l), i.e.

$\begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + {L({{2K} - 2})}}}^{(1)}p_{l,{i + {L({{2K} - 2})}}}^{(2)}\varphi_{l,{i + {L({{2K} - 2})}}}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + {L({{2K} - 1})}}}^{(1)}p_{l,{i + {L({{2K} - 1})}}}^{(2)}\varphi_{l,{i + {L({{2K} - 1})}}}}} \end{bmatrix},$

corresponds to the k^(th) panel where p_(l,i+L(2k−2)) ⁽¹⁾ and p_(l,i+L(2k−2)) ⁽²⁾ k=1, . . . , K are wide-band and sub-band amplitude coefficients for the i^(th) beam of the k^(th) panel for first polarized antenna elements, p_(l,i+L(2k−1)) ⁽¹⁾ and p_(l,i+L(2k−1)) ⁽²⁾ k=1, . . . , K are wide-band and sub-band amplitude coefficients for the i^(th) beam of the k^(th) panel for second polarized antenna elements, φ_(l,i+L(2k−2)), φ_(l,i+L(2k−1)) k=1, . . . , K are phase shift coefficients for the i^(th) beam of the k^(th) panel for first and second polarized antenna elements, respectively, and v_(i) _(1,1) _(d+i) is the 2D DFT virtualization coefficient for the i^(th) beam. The Σ_(i=0) ^(L−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i+L(2k−2)) ⁽¹⁾p_(l,i+L(2k−2)) ⁽²⁾φ_(l,i+L(2k−2)) are beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for the first polarized antenna elements and Σ_(i=0) ^(L−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i+L(2k−1)) ⁽¹⁾p_(l,i+L(2k−1)) ⁽²⁾φ_(l,i+L(2k−1)) are the beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for the second polarized antenna elements. Hence, for each layer of transmission, the L selected beams are combined with different sets of amplitude and phase shift coefficients per polarization in each panel.

In the above-disclosed scheme, the assignment of amplitude and phase shift coefficients is with respect to the strongest beam which is identified per layer across both polarizations and all panels. This may create substantial signaling overhead as a result of a PMI reporting requirement of 2KL coefficients for each of the i_(1,4,l), i_(2,1,l) and i_(2,2,l) parameters.

An alternative scheme with significantly reduced signaling overhead yet using independent beams per panel is to assign amplitude and phase shift coefficients per panel with respect to the strongest beam in that panel. In this scheme, a set of L beam groups are first selected to be shared across polarizations, layers and panels. The selection of those initial L beams can be performed through transmission across all panels or from a specific panel The strongest beam is then identified per layer and per panel, across both polarizations where a set of amplitude and phase shift coefficients are applied to beams accordingly per panel with respect to the identified strongest beam in that panel. PMI reporting is accomplished by the UE reporting i_(1,1) and i_(1,2) to indicate L beams/beam groups, i_(1,3,l) to indicate the strongest coefficient on layer l, i_(1,4,l) to indicate wideband amplitude coefficients for layer l, i_(2,1,l) to indicate the phase coefficient for layer l, and i_(2,2,l) to indicate the sub-band amplitude coefficient for layer l. In this scheme, the i_(1,3,l) parameter takes K values where K is the number of panels. That is, for each layer of transmission, there are K identified strongest beams, one per panel. The definition of i_(1,3,l) can be modified to i_(1,3,l,k) to indicate the strongest beam for layer l on panel k. In this scheme, the Type II multi-panel codebook is defined in Equation (62) as follows.

$\begin{matrix} {W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{(R)} = {\frac{1}{\sqrt{R}}\left\lbrack {\begin{matrix} \begin{matrix} W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1} & \ldots \end{matrix} & \left. W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{R} \right\rbrack \end{matrix},} \right.}} & (62) \end{matrix}$

In Equation (62), each column of W_(q) ₁ _(,q) ₂ _(,n) ₁ _(,n) ₂ _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,R) ^((R)) matrix indicates the precoding coefficients for each layer of transmission. The column l corresponding to precoding coefficient of layer l is defined in Equation (63) as follows.

$\begin{matrix} {{W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,i}}^{l} = \frac{1}{\sqrt{N_{1}N_{2}{\sum}_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)}p_{l,i}^{(2)}} \right)^{2}}}}\text{ }{{{\begin{bmatrix} \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{({1,1})}p_{l,i}^{({2,1})}\varphi_{l,i}^{(1)}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{({1,1})}p_{l,{i + L}}^{({2,1})}\varphi_{l,{i + L}}^{(1)}}} \end{bmatrix} \\  \vdots \\ \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{({1,K})}p_{l,i}^{({2,K})}\varphi_{l,i}^{(K)}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{({1,K})}p_{l,{i + L}}^{({2,K})}\varphi_{l,{i + L}}^{(K)}}} \end{bmatrix} \end{bmatrix}l} = 1},\ldots,R}} & (63) \end{matrix}$

where the k^(th) matrix block in Equation (63) for W_(q) ₁ _(,q) ₂ _(,n) ₁ _(,n) ₂ _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,l) ^(l), i.e.,

$\begin{bmatrix} {{\sum}_{i = 0}^{L - 1}v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{({1,k})}p_{l,i}^{({2,k})}\varphi_{l,i}^{(k)}} \\ {{\sum}_{i = 0}^{L - 1}v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{({1,k})}p_{l,{i + L}}^{({2,k})}\varphi_{l,{i + L}}^{(k)}} \end{bmatrix},$

corresponds to the k^(th) panel where p_(l,i) ^((1,k)) and p_(l,i) ^((2,k)) k=1, . . . , K are wide-band and sub-band amplitude coefficients for the i^(th) beam of k^(th) panel for the first polarized antenna elements with respect to the strongest beam on panel k, p_(l,i+L) ^((1,k)) and p_(l,i+L) ^((2,k)) k=1, . . . , K are wide-band and sub-band amplitude coefficients for the i^(th) beam of k^(th) panel for the second polarized antenna elements with respect to the strongest beam on panel k, φ_(l,i) ^((k)), φ_(l,i) ^((k)) k=1, . . . , K are phase shift coefficients for the i^(th) beam of the k^(th) panel for the first and second polarized antenna elements with respect to the strongest beam on panel k, respectively, and v_(m) ₁ _((i)) _(,m) ₂ _((i)) is the 2D DFT virtualization coefficient for the i^(th) beam. The Σ_(i=0) ^(L−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i) ^((1,k))p_(l,i) ^((2,k))φ_(l,i) ^((k)) are the beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for first polarized antenna elements and Σ_(i=0) ^(L−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i+L) ^((1,k))p_(l,i+L) ^((2,k))φ_(l,i+L) ^((k)) are the beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for the second polarized antenna elements.

Similarly, for the Type II port selection, the enhanced multi-panel codebook design is defined in Equations (64) and (65) as follows.

$\begin{matrix} {W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{(R)} = {\frac{1}{\sqrt{R}}\left\lbrack \begin{matrix} \begin{matrix} W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1} & \ldots \end{matrix} & \left. W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{R} \right\rbrack \end{matrix} \right.}} & (64) \end{matrix}$ where ${W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,i}}^{l} = \frac{1}{\sqrt{{\sum}_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)}p_{l,i}^{(2)}} \right)^{2}}}}\text{ }{{{\begin{bmatrix} \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{({1,1})}p_{l,i}^{({2,1})}\varphi_{l,i}^{(1)}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + L}}^{({1,1})}p_{l,{i + L}}^{({2,1})}\varphi_{l,{i + L}}^{(1)}}} \end{bmatrix} \\  \vdots \\ \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{({1,K})}p_{l,i}^{({2,K})}\varphi_{l,i}^{(K)}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + L}}^{({1,K})}p_{l,{i + L}}^{({2,K})}\varphi_{l,{i + L}}^{(K)}}} \end{bmatrix} \end{bmatrix}l} = 1},\ldots,R}$

where the k^(th) matrix block in Equation (65) for W_(i) _(1,1) _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,l) ^(l), i.e.,

$\begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{({1,k})}p_{l,i}^{({2,k})}\varphi_{l,i}^{(k)}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + L}}^{({1,k})}p_{l,{i + L}}^{({2,k})}\varphi_{l,{i + L}}^{(k)}}} \end{bmatrix},$

corresponds to the k^(th) panel where p_(l,i) ^((1,k)) and p_(l,i) ^((2,k)) k=1, . . . , K are wide-band and sub-band amplitude coefficients for the i^(th) beam of the k^(th) panel for the first polarized antenna elements with respect to the strongest beam on panel k, p_(l,i+L) ^((1,k)) and p_(l,i+L) ^((2,k)) k=1, . . . , K are wide-band and sub-band amplitude coefficients for the i^(th) beam of the k^(th) panel for the second polarized antenna elements with respect to the strongest beam on panel k, φ_(l,i) ^((k)), φ_(l,i+L) ^((k)) k=1, . . . , K are phase shift coefficients for the i^(th) beam of the k^(th) panel for first and second polarized antenna elements with respect to the strongest beam on panel k, respectively, and, and v_(i) _(1,1) _(d+i) is the 2D DFT virtualization coefficient for the i^(th) beam. The Σ_(i=0) ^(L−1)v_(i) _(1,1) _(d+i)p_(l,i) ^((1,k))p_(l,i) ^((2,k))φ_(l,i) ^((k)) are the beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for the first polarized antenna elements and Σ_(i=0) ^(L−1)v_(i) _(1,1) _(d+i)p_(l,i+L) ^((1,k))p_(l,i+L) ^((2,k))φ_(l,i+L) ^((k)) are the beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for the second polarized antenna elements.

Another approach is to allow different initial L beam selections per different panel. In this scheme, the signaling overhead is reduced by defining only one set of the amplitude and phase shift coefficients applicable to different panels as these coefficients scale the other beams with respect to the strongest beam in each panel. Specifically, different beams are generated per layer, per polarization and per panel using a linear combination of L specific selected beams/beam groups per panel using one set of amplitude and phase shift coefficients. In this scheme, there are a total of KL beams/groups of beam selections for K panels (i.e., L beams per panel). PMI reporting is accomplished by the UE reporting i_(1,1) and i_(1,2) to indicate KL beams/beam groups, i_(1,3,l) to indicate the strongest coefficient on layer l, i_(1,4,l) to indicate wideband amplitude coefficients for layer l, i_(2,1,l) to indicate the phase coefficient for layer l, and i_(2,2,l) to indicate the sub-band amplitude coefficient for layer l. In this scheme, each i_(1,1), i_(1,2) and i_(1,3,l) parameter takes K values where K is the number of panels. That is, for each layer of transmission, there are K sets of L selected beams and K identified strongest beams (i.e., one per panel). The definition of i_(1,1), i_(1,2) and i_(1,3,l) can be modified to i_(1,1,k), i_(1,2,k) and i_(1,3,l,k) to indicate the beams for layer l on panel k. The Type II multi-panel codebook is defined in Equation (66) as follows.

$\begin{matrix} {W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{(R)} = {\frac{1}{\sqrt{R}}\left\lbrack {\begin{matrix} \begin{matrix} W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1} & \ldots \end{matrix} & \left. W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{R} \right\rbrack \end{matrix},} \right.}} & (66) \end{matrix}$

where each column of W_(q) ₁ _(,q) ₂ _(,n) ₁ _(,n) ₂ _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,R) ^((R)) matrix indicates the precoding coefficients for each layer of transmission. The column l corresponding to precoding coefficient of layer l is defined in Equation (67) as follows.

$\begin{matrix} {{W_{q_{1},q_{2},n_{1},n_{2},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,l}}^{l} = \frac{1}{\sqrt{N_{1}N_{2}{\sum}_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)}p_{l,i}^{(2)}} \right)^{2}}}}\text{ }{{{\begin{bmatrix} \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{({1,1})}p_{l,i}^{({2,1})}\varphi_{l,i}^{(1)}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{({1,1})}p_{l,{i + L}}^{({2,1})}\varphi_{l,{i + L}}^{(1)}}} \end{bmatrix} \\  \vdots \\ \begin{bmatrix} {\sum\limits_{i = {{({K - 1})}L}}^{{KL} - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{({1,K})}p_{l,i}^{({2,K})}\varphi_{l,i}^{(K)}}} \\ {\sum\limits_{i = {{({K - 1})}L}}^{{KL} - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{({1,K})}p_{l,{i + L}}^{({2,K})}\varphi_{l,{i + L}}^{(K)}}} \end{bmatrix} \end{bmatrix}l} = 1},\ldots,R}} & (67) \end{matrix}$

where the k^(th) matrix block in Equation (67) for W_(q) ₁ _(,q) ₂ _(,n) ₁ _(,n) ₂ _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,l) ^(l), i.e.,

$\begin{bmatrix} {\sum\limits_{i = {{({K - 1})}L}}^{{KL} - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,i}^{({1,K})}p_{l,i}^{({2,K})}\varphi_{l,i}^{(K)}}} \\ {\sum\limits_{i = {{({K - 1})}L}}^{{KL} - 1}{v_{m_{1}^{(i)},m_{2}^{(i)}}p_{l,{i + L}}^{({1,K})}p_{l,{i + L}}^{({2,K})}\varphi_{l,{i + L}}^{(K)}}} \end{bmatrix},$

corresponds to the k^(th) panel where p_(l,i) ^((1,k)) and p_(l,i) ^((2,k)) k=1, . . . , K are wide-band and sub-band amplitude coefficients for the i^(th) beam of the k^(th) panel for the first polarized antenna elements with respect to the strongest beam on panel k, p_(l,i+L) ^((1,k)) and p_(l,i+L) ^((2,k)) k=1, . . . , K are wide-band and sub-band amplitude coefficients for the i^(th) beam of the k^(th) panel for the second polarized antenna elements with respect to the strongest beam on panel k, φ_(l,i) ^((k)), φ_(l,i+L) ^((k)) k=1, . . . , K are phase shift coefficients for the i^(th) beam of the k^(th) panel for the first and second polarized antenna elements with respect to the strongest beam on panel k, respectively, and v_(m) ₁ _((i)) _(,m) ₂ _((i)) is the 2D DFT virtualization coefficient for the i^(th) beam. The Σ_(i=(k−1)L) ^(kL−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i) ^((1,k))p_(l,i) ^((2,k))φ_(l,i) ^((k)) are the beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for the first polarized antenna elements that is derived by linear combination of ((k−1)L)^(th) to (kL−1)^(th) beams using p_(l,i) ^((1,k)), p_(l,i) ^((2,k)) and φ_(l,i) ^((k)) coefficients and Σ_(i=(k−1)L) ^(kL−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i+L) ^((1,k))p_(l,i+L) ^((2,k))φ_(l,i+L) ^((k)) are the beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for the second polarized antenna elements that are derived by linear combination of ((k−1)L)^(th) to (kL−1)^(th) beams using p_(l,i+L) ^((1,k)), p_(l,i+L) ^((2,k)) and φ_(l,i+L) ^((k)) coefficients.

Similarly, for the Type II port selection, the enhanced multi-panel codebook design is defined in Equations (68) and (69) as follows.

$\begin{matrix} {W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{(R)} = {\frac{1}{\sqrt{R}}\left\lbrack \begin{matrix} \begin{matrix} W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,1}}^{1} & \ldots \end{matrix} & \left. W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,R}}^{R} \right\rbrack \end{matrix} \right.}} & (68) \end{matrix}$ where $\begin{matrix} {{W_{i_{1,1},p_{l}^{(1)},p_{l}^{(2)},i_{2,1,l}}^{l} = \frac{1}{\sqrt{{\sum}_{i = 0}^{{2L} - 1}\left( {p_{l,i}^{(1)}p_{l,i}^{(2)}} \right)^{2}}}}\text{ }{{{\begin{bmatrix} \begin{bmatrix} {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{({1,1})}p_{l,i}^{({2,1})}\varphi_{l,i}^{(1)}}} \\ {\sum\limits_{i = 0}^{L - 1}{v_{{i_{1,1}d} + i}p_{l,{i + L}}^{({1,1})}p_{l,{i + L}}^{({2,1})}\varphi_{l,{i + L}}^{(1)}}} \end{bmatrix} \\  \vdots \\ \begin{bmatrix} {\sum\limits_{i = {{({K - 1})}L}}^{{KL} - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{({1,K})}p_{l,i}^{({2,K})}\varphi_{l,i}^{(K)}}} \\ {\sum\limits_{i = {{({K - 1})}L}}^{{KL} - 1}{v_{{i_{1,1}d} + i}p_{l,{i + L}}^{({1,K})}p_{l,{i + L}}^{({2,K})}\varphi_{l,{i + L}}^{(K)}}} \end{bmatrix} \end{bmatrix}l} = 1},\ldots,R}} & (69) \end{matrix}$

where the k^(th) matrix block in Equation (69) for W_(i) _(1,1) _(,p) _(l) ₍₁₎ _(,p) _(l) ₍₂₎ _(,i) _(2,1,l) ^(l), i.e.

$\begin{bmatrix} {\sum\limits_{i = {{({k - 1})}L}}^{{kL} - 1}{v_{{i_{1,1}d} + i}p_{l,i}^{({1,k})}p_{l,i}^{({2,k})}\varphi_{l,i}^{(k)}}} \\ {\sum\limits_{i = {{({k - 1})}L}}^{{kL} - 1}{v_{{i_{1,1}d} + i}p_{l,{i + L}}^{({1,k})}p_{l,{i + L}}^{({2,k})}\varphi_{l,{i + L}}^{(k)}}} \end{bmatrix},$

corresponds to the k^(th) panel where p_(l,i) ^((1,k)) and p_(l,i) ^((2,k)) k=1, . . . ,K are wide-band and sub-band amplitude coefficients for the i^(th) beam of the k^(th) panel for the first polarized antenna elements with respect to the strongest beam on panel k, p_(l,i+L) ^((1,k)) and p_(l,i+L) ^((2,k)) k=1, . . . , K are wide-band and sub-band amplitude coefficients for the i^(th) beam of the k^(th) panel for the second polarized antenna elements with respect to the strongest beam on panel k, φ_(l,i) ^((k)), φ_(l,i+L) ^((k)) k=1, . . . , K are phase shift coefficients for the i^(th) beam of the k^(th) panel for the first and second polarized antenna elements with respect to the strongest beam on panel k, respectively, and v_(m) ₁ _((i)) _(,m) ₂ _((i)) is the 2D DFT virtualization coefficient for the i^(th) beam. The Σ_(i=(k−1)L) ^(kL−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i) ^((1,k))p_(l,i) ^((2,k))φ_(l,i) ^((k)) are the beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for the first polarized antenna elements that are derived by linear combination of ((k−1)L)^(th) to (kL−1)^(th) beams using p_(l,i) ^((1,k)), p_(l,i) ^((2,k)) and φ_(l,i) ^((k)) coefficients and Σ_(i=(k−1)L) ^(kL−1)v_(m) ₁ _((i)) _(,m) ₂ _((i)) p_(l,i+L) ^((1,k))p_(l,i+L) ^((2,k))φ_(l,i+L) ^((k)) are the beamforming virtualization coefficients of N₁N₂ ports in the k^(th) panel for the second polarized antenna elements that are derived by linear combination of ((k−1)L)^(th) to (kL−1)^(th) beams using p_(l,i+L) ^((1,k)), p_(l,i+L) ^((2,k)) and φ_(l,i+L) ^((k)) coefficients.

SRS Enhancements

FIG. 9 depicts an example method for SRS transmissions. At step 910, a UE determines that an SRS is to be transmitted to a gNB. For example, the UE may be configured to perform periodic SRS transmissions. Additionally or alternatively, the UE may perform an SRS transmission to the gNB in response to a request from the gNB for an SRS transmission or prior to sending a different transmission to a gNB or other UE.

At step 920 the UE determines one or more power control parameters of the SRS resource in response to the determination that an SRS is to be transmitted to the gNB. For instance, instead of the power control parameters being all pre-configured, one or more of the power control parameters may be determined prior to the transmission of the SRS. Additionally or alternatively, the UE may be configured to determine spatial relation information, such as a beam direction in FR2 transmissions, in response to the determination that an SRS is to be transmitted to the gNB.

In some embodiments, the determined one or more power control parameters and/or spatial relation information are used to reconfigure SRS resource sets prior to transmission across TRPs in order to update one or more power control parameters. The update of the one or more control parameters and/or spatial relation information may be performed using a medium access control (MAC) control element (MAC-CE) and/or a dynamic control element (DCI).

In some embodiments, the one or more power control parameters may comprise the fractional power control multiplier, α_(SRS,b,f,c)(q_(s)). In some embodiments, the nominal UE transmit power and pathloss reference signal are semi-statically configured for the SRS resource set based on a worst TRP transmission while the fractional power control multiplier is determined dynamically prior to the transmission, thereby enabling per TRP SRS power control to suppress inter-TRP cross-SRS interference.

In some embodiments, the one or more power control parameters comprise the pathloss reference signal, q_(d) based on a TRP prior transmission to different TRPs. The UE may measure a path loss separately for each TRP transmission and determine the pathloss reference signal based on a previously measured SRS path loss.

In some embodiments, the one or more control parameters may comprise the nominal UE transmit power P_(0_SRS,b,f,c)(q_(s)). In some embodiments, the pathloss reference signal and fraction power control multiplier are semi-statically configured for the SRS resource set while the nominal transmit power is dynamically determined prior to transmission to different TRPs.

Any of the aforementioned power control parameters may be dynamically determined prior to transmission, alone or in combination. For example, the UE may be configured to dynamically determine one power control parameter, two power control parameters, or any number of power control parameters.

In some embodiments, determining the one or more power control parameters and/or spatial relation information comprises selecting a set of power control parameters and/or spatial relation information from a plurality of RRC configured power control parameter sets. For example, the sets may comprise a combination of pathloss reference signal and other power control parameters that are associated with the pathloss reference signal. The UE may then select a set of power control parameter based on a previously measured path loss. A DCI or MAC CE may be used to indicate the power control parameter set to the UE prior to transmission across TRPs. For instance, a MAC CE may be used to update and/or indicate a pathloss reference signal dynamically prior to transmission to different TRPs. Identifying the pathloss reference signal would thus identify the corresponding power control parameter set.

At step 930, the UE transmits the SRS with the dynamically determined one or more power control parameters to the gNB. For example, the UE may compute the SRS transmission power based on the power control parameters and transmit the SRS to the gNB using the calculated transmission power.

In some embodiments, inter-TRP cross-SRS interference is further avoided by assigning orthogonal SRS resources among neighboring cells. The orthogonal resources reduce the probability of collision at the cost of reducing a number of configurable SRS resources per cell and degrading SRS performance.

In some embodiments, inter-TRP cross-SRS interference is further avoided by using Code Division Multiplexing (CDM). For instance, SRS resources may be shared between multiple UEs and/or multiple ports of a UE with an application of an Orthogonal Cover Code (OCC). In such embodiments, configuration data may identify SRS resources and corresponding TRPs with power control parameters and/or spatial relation information. The gNB may indicate to the UE that an OCC is to be used by using a new field or reusing existing fields in DCI, such as DCI format 0_1 and DCI format 1_1. The indication implicitly informs the UE about the interference of neighboring cells and that an OCC code is to be used on its SRS transmission.

FIG. 5 depicts an example of a multi-TRP scenario where each UE utilizes a plurality of resources to perform the multi-TRP transmissions. System 500 comprises a multi-TRP system with M TRPs. Each UE is configured with M times the number of resources as the UE would be configured with in a single TRP scenario. Thus, each UE is allocated M orthogonal Zadoff-Chu sequences for use in transmission to the M TRPs with each sequence corresponding to a specific TRP. The SRS transmissions across different UE antenna ports towards each TRP may be performed through application of a cyclic shift on the allocated base sequences for that specific TRP.

As each UE is allocated with M sequences, a number of available orthogonal sequence that can be allocated to other UEs decreases compared to the single TRP scenario. However, with the introduction of the CDM concept to the SRS signals, the same sequence can now be assigned to other UEs for transmission toward the same TRP while sharing the same frequency and time resources.

FIG. 6 depicts an example application of OCC codes. System 600 comprises two UEs, each with a comb size of two. The TRP transmission of the two UEs in FIG. 6 are code division multiplexed with a same SRS sequence s(n)=r _(u,v)(n). At the gNB, Y₁ and Y₂ are the received signals at subcarriers 0 and 2 respectively. The signals are received at a single antenna. The signals are defined as:

Y ₁ =h ₁ S(0)+h ₂ S(0)

Y ₂ =h ₁ S(2)−h ₂ S(2),

Solving the above equations, the channel estimates h₁ (between UE 1 and TRP 1) and h₂ (between UE2 and TRP 1) are simply derived as:

$h_{1} = \frac{{{S(2)}Y_{1}} + {{S(0)}Y_{2}}}{2{S(0)}{S(2)}}$ ${h_{2} = \frac{{{S(2)}Y_{1}} - {{S(0)}Y_{2}}}{2{S(0)}{S(2)}}},$

The example of FIG. 6 depicts application of the OCC to a single TRP transmission of the two UEs. As depicted in FIG. 5 , the same method may be applied to a second resource used for a second TRP transmission of the two UEs. Thus, UE_(i) may be configured with M resources for M TRP transmissions with each resource being used by UE_(j) for M TRP transmissions towards the same TRP.

In some embodiments, a UE is configured with one SRS base sequence that is shared for SRS transmissions towards multiple TRPs over non-overlapping frequency resources, such as through a comb structure, frequency hopping, or RB-level partial frequency sounding techniques. Similar to the implementation of FIG. 6 , the SRS transmissions across different UE antenna ports sharing the same time and frequency resources towards a TRP is performed using cyclic shifts on the allocated base sequence.

FIG. 7 depicts an example of a multi-TRP scenario where each UE utilizes a single SRS base sequence to perform the multi-TRP transmissions. System 700 comprises two UEs transmitting to M TRPs. UE_(i) uses a single SRS base sequence, s(n)=r _(u,v)(n), for transmissions to a plurality of TRPs, with the single SRS base sequence being transmitted over non-overlapping frequency resources. UE_(j) uses the same SRS base sequence, s(n)=r _(u,v)(n), for transmissions to the same plurality of TRPs over the same non-overlapping frequency resources. Different OCCs are applied to the transmissions of UE_(i) and UE_(j) to provide orthogonality and suppress cross-SRS interference. The channel estimates are derived in the same way as described above with respect to FIG. 6 .

In some embodiments, each UE is configured with the same configured SRS resources as for a single TRP scenario and those resources are shared for SRS transmission toward multiple TRPs. Code division multiplexing may then be used to suppress cross-SRS interference for the different resources used by the different UEs.

FIG. 8 depicts an example application of OCC codes. System 800 comprises two UEs, each with a comb size of two. The UEs are code division multiplexed with different SRS sequences s₁(n)=r _(u,v)(n) and s₂(n)=r _(u′,v′)(n). At gNB, Y₁ and Y₂ are the received signal at subcarrier 0 and 2 respectively as follows:

Y ₁ =h ₁ S(0)+h ₂ S(0)

Y ₂ =h ₁ S(2)−h ₂ S(2),

where S₁ is SRS sequence of one UE (i.e. UE 1), and S₂ is SRS sequence allocated to another UE (i.e. UE 2). This corresponds to the configuration where these two UEs are CDM'ed using same time and frequency resources. Since ZC sequences are constant modulus in frequency domain (i.e. |S₂(0)|=|S₂(2|), the channel estimates h₁ and h₂ are derived as:

$h_{1} = \frac{{{S_{2}^{\star}(0)}Y_{1}} + {{S_{2}^{\star}(2)}Y_{2}}}{{{S_{1}(0)}{S_{2}^{\star}(0)}} + {{S_{1}(2)}{S_{2}^{\star}(2)}}}$ $h_{2} = \frac{{{S_{1}^{\star}(0)}Y_{1}} - {{S_{1}^{\star}(2)}Y_{2}}}{{{S_{2}(0)}{S_{1}^{\star}(0)}} + {{S_{2}(2)}{S_{1}^{\star}(2)}}}$

The constant modulus of ZC sequence in frequency domain enables orthogonal sequences with cyclic shifts. Considering s₁(n)=s₂(n)e^(jαn), it can be shown that the denominator of h₁ renamed to A=S₁(0)S₂*(0)+S₁(2)S₂*(2) and the denominator of h₂ renamed to B=S₂(0)S₁*(0)+S₂(2)S₁*(2) have equal absolute values so preventing noise enhancement in channel estimation:

A=|S ₁(0)|²(1+e ^(j2α))

B=|S ₁(0)|²(1+e ^(−j2α))

Thus, multiple UEs can be multiplexed over the same time and frequency resources in a multi-TRP scenario regardless of whether those UEs are allocated the same SRS sequence or not. This allows the multiplexing to be applied to a same resource used for transmissions to different TRPs from a single UE.

While FIG. 6-8 depict code division multiplexing across two UEs, the implementations described above may be extended for SRS transmissions to N UEs when SRS transmission occurs over at least N symbols.

FIG. 10 is a block diagram of an electronic device in a network environment 1000, according to an embodiment. Referring to FIG. 10 , an electronic device 1001 in a network environment 1000 may communicate with an electronic device 1002 via a first network 1098 (e.g., a short-range wireless communication network), or an electronic device 1004 or a server 1008 via a second network 1099 (e.g., a long-range wireless communication network). The electronic device 1001 may communicate with the electronic device 1004 via the server 1008. The electronic device 1001 may include a processor 1020, a memory 1030, an input device 1040, a sound output device 1055, a display device 1060, an audio module 1070, a sensor module 1076, an interface 1077, a haptic module 1079, a camera module 1080, a power management module 1088, a battery 1089, a communication module 1090, a subscriber identification module (SIM) card 1096, or an antenna module 1094. In one embodiment, at least one (e.g., the display device 1060 or the camera module 1080) of the components may be omitted from the electronic device 1001, or one or more other components may be added to the electronic device 1001. Some of the components may be implemented as a single integrated circuit (IC). For example, the sensor module 1076 (e.g., a fingerprint sensor, an iris sensor, or an illuminance sensor) may be embedded in the display device 1060 (e.g., a display).

The processor 1020 may execute, for example, software (e.g., a program 1040) to control at least one other component (e.g., a hardware or a software component) of the electronic device 1001 coupled with the processor 1020 and may perform various data processing or computations, such as for CSI in multi-TRP CJT as disclosed herein. As at least part of the data processing or computations, the processor 1020 may load a command or data received from another component (e.g., the sensor module 1046 or the communication module 1090) in volatile memory 1032, process the command or the data stored in the volatile memory 1032, and store resulting data in non-volatile memory 1034. The processor 1020 may include a main processor 1021 (e.g., a central processing unit (CPU) or an application processor (AP)), and an auxiliary processor 1023 (e.g., a graphics processing unit (GPU), an image signal processor (ISP), a sensor hub processor, or a communication processor (CP)) that is operable independently from, or in conjunction with, the main processor 1021. Additionally or alternatively, the auxiliary processor 1023 may be adapted to consume less power than the main processor 1021, or execute a particular function. The auxiliary processor 1023 may be implemented as being separate from, or a part of, the main processor 1021.

The auxiliary processor 1023 may control at least some of the functions or states related to at least one component (e.g., the display device 1060, the sensor module 1076, or the communication module 1090) among the components of the electronic device 1001, instead of the main processor 1021 while the main processor 1021 is in an inactive (e.g., sleep) state, or together with the main processor 1021 while the main processor 1021 is in an active state (e.g., executing an application). The auxiliary processor 1023 (e.g., an image signal processor or a communication processor) may be implemented as part of another component (e.g., the camera module 1080 or the communication module 1090) functionally related to the auxiliary processor 1023.

The memory 1030 may store various data used by at least one component (e.g., the processor 1020 or the sensor module 1076) of the electronic device 1001. The various data may include, for example, software (e.g., the program 1040) and input data or output data for a command related thereto. The memory 1030 may include the volatile memory 1032 or the non-volatile memory 1034.

The program 1040 may be stored in the memory 1030 as software, and may include, for example, an operating system (OS) 1042, middleware 1044, or an application 1046.

The input device 1050 may receive a command or data to be used by another component (e.g., the processor 1020) of the electronic device 1001, from the outside (e.g., a user) of the electronic device 1001. The input device 1050 may include, for example, a microphone, a mouse, or a keyboard.

The sound output device 1055 may output sound signals to the outside of the electronic device 1001. The sound output device 1055 may include, for example, a speaker or a receiver. The speaker may be used for general purposes, such as playing multimedia or recording, and the receiver may be used for receiving an incoming call. The receiver may be implemented as being separate from, or a part of, the speaker.

The display device 1060 may visually provide information to the outside (e.g., a user) of the electronic device 1001. The display device 1060 may include, for example, a display, a hologram device, or a projector and control circuitry to control a corresponding one of the display, hologram device, and projector. The display device 1060 may include touch circuitry adapted to detect a touch, or sensor circuitry (e.g., a pressure sensor) adapted to measure the intensity of force incurred by the touch.

The audio module 1070 may convert a sound into an electrical signal and vice versa. The audio module 1070 may obtain the sound via the input device 1050 or output the sound via the sound output device 1055 or a headphone of an external electronic device 1002 directly (e.g., wired) or wirelessly coupled with the electronic device 1001.

The sensor module 1076 may detect an operational state (e.g., power or temperature) of the electronic device 1001 or an environmental state (e.g., a state of a user) external to the electronic device 1001, and then generate an electrical signal or data value corresponding to the detected state. The sensor module 1076 may include, for example, a gesture sensor, a gyro sensor, an atmospheric pressure sensor, a magnetic sensor, an acceleration sensor, a grip sensor, a proximity sensor, a color sensor, an infrared (IR) sensor, a biometric sensor, a temperature sensor, a humidity sensor, or an illuminance sensor.

The interface 1077 may support one or more specified protocols to be used for the electronic device 1001 to be coupled with the external electronic device 1002 directly (e.g., wired) or wirelessly. The interface 1077 may include, for example, a high-definition multimedia interface (HDMI), a universal serial bus (USB) interface, a secure digital (SD) card interface, or an audio interface.

A connecting terminal 1078 may include a connector via which the electronic device 1001 may be physically connected with the external electronic device 1002. The connecting terminal 1078 may include, for example, an HDMI connector, a USB connector, an SD card connector, or an audio connector (e.g., a headphone connector).

The haptic module 1079 may convert an electrical signal into a mechanical stimulus (e.g., a vibration or a movement) or an electrical stimulus which may be recognized by a user via tactile sensation or kinesthetic sensation. The haptic module 1079 may include, for example, a motor, a piezoelectric element, or an electrical stimulator.

The camera module 1080 may capture a still image or moving images. The camera module 1080 may include one or more lenses, image sensors, image signal processors, or flashes.

The power management module 1088 may manage power supplied to the electronic device 1001. The power management module 1088 may be implemented as at least part of, for example, a power management integrated circuit (PMIC).

The battery 1089 may supply power to at least one component of the electronic device 1001. The battery 1089 may include, for example, a primary cell which is not rechargeable, a secondary cell which is rechargeable, or a fuel cell.

The communication module 1090 may support establishing a direct (e.g., wired) communication channel or a wireless communication channel between the electronic device 1001 and the external electronic device (e.g., the electronic device 1002, the electronic device 1004, or the server 1008) and performing communication via the established communication channel. The communication module 1090 may include one or more communication processors that are operable independently from the processor 1020 (e.g., the AP) and supports a direct (e.g., wired) communication or a wireless communication. The communication module 1090 may include a wireless communication module 1092 (e.g., a cellular communication module, a short-range wireless communication module, or a global navigation satellite system (GNSS) communication module) or a wired communication module 1094 (e.g., a local area network (LAN) communication module or a power line communication (PLC) module). A corresponding one of these communication modules may communicate with the external electronic device via the first network 1098 (e.g., a short-range communication network, such as Bluetooth™, wireless-fidelity (Wi-Fi) direct, or a standard of the Infrared Data Association (IrDA)) or the second network 1099 (e.g., a long-range communication network, such as a cellular network, the Internet, or a computer network (e.g., LAN or wide area network (WAN)). These various types of communication modules may be implemented as a single component (e.g., a single IC), or may be implemented as multiple components (e.g., multiple ICs) that are separate from each other. The wireless communication module 1092 may identify and authenticate the electronic device 1001 in a communication network, such as the first network 1098 or the second network 1099, using subscriber information (e.g., international mobile subscriber identity (IMSI)) stored in the subscriber identification module 1096.

The antenna module 1097 may transmit or receive a signal or power to or from the outside (e.g., the external electronic device) of the electronic device 1001. The antenna module 1097 may include one or more antennas, and, therefrom, at least one antenna appropriate for a communication scheme used in the communication network, such as the first network 1098 or the second network 1099, may be selected, for example, by the communication module 1090 (e.g., the wireless communication module 1092). The signal or the power may then be transmitted or received between the communication module 1090 and the external electronic device via the selected at least one antenna.

Commands or data may be transmitted or received between the electronic device 1001 and the external electronic device 1004 via the server 1008 coupled with the second network 1099. Each of the electronic devices 1002 and 1004 may be a device of a same type as, or a different type, from the electronic device 1001. All or some of operations to be executed at the electronic device 1001 may be executed at one or more of the external electronic devices 1002, 1004, or 1008. For example, if the electronic device 1001 should perform a function or a service automatically, or in response to a request from a user or another device, the electronic device 1001, instead of, or in addition to, executing the function or the service, may request the one or more external electronic devices to perform at least part of the function or the service. The one or more external electronic devices receiving the request may perform the at least part of the function or the service requested, or an additional function or an additional service related to the request and transfer an outcome of the performing to the electronic device 1001. The electronic device 1001 may provide the outcome, with or without further processing of the outcome, as at least part of a reply to the request. To that end, a cloud computing, distributed computing, or client-server computing technology may be used, for example.

FIG. 11 shows a system including a UE 1105 and a gNB 1110, in communication with each other. The UE may include a radio 1115 and a processing circuit (or a means for processing) 1120, which may perform various methods disclosed herein, e.g., the method illustrated in FIG. 1 . For example, the processing circuit 1120 may receive, via the radio 1115, transmissions from the network node (gNB) 1110, and the processing circuit 1120 may transmit, via the radio 1115, signals to the gNB 1110.

While the present disclosure has been described with reference to certain embodiments, various changes may be made without departing from the spirit and the scope of the disclosure, which is defined, not by the detailed description and embodiments, but by the appended claims and their equivalents. 

What is claimed is:
 1. A method, comprising: determining, at a user equipment (UE), that a Sounding Reference Signal (SRS) resource is to be transmitted to a base station (gNB); in response to determining that the SRS resource is to be transmitted to the gNB, determining one or more power control parameters of the SRS resource; and transmitting the SRS resource with the determined one or more power control parameters to the gNB.
 2. The method of claim 1, further comprising, in response to determining that the SRS resource is to be transmitted to the gNB, determining spatial relation information of the SRS resource.
 3. The method of claim 1, wherein determining the one or more power control parameters of the SRS resource comprises determining a fractional power control multiplier.
 4. The method of claim 3, wherein a nominal UE transmit power and a pathloss reference signal are configured for an SRS resource set that includes the SRS resource based on a worst transmission and reception point (TRP) transmission.
 5. The method of claim 1, wherein determining the one or more power control parameters of the SRS resource comprises measuring a path loss for transmitting to the gNB and determining a pathloss reference signal from the measured path loss.
 6. The method of claim 1, wherein determining the one or more power control parameters of the SRS resource comprises determining a nominal UE transmit power for a TRP transmission.
 7. The method of claim 6, wherein a single pathloss reference signal and a single fractional power control multiplier are configured for an SRS resource set that includes the SRS resource.
 8. The method of claim 1, further comprising updating the one or more power control parameters using a medium access control (MAC) control element (MAC-CE) or dynamic control element (DCI).
 9. The method of claim 1, wherein multiple options for the one or more power control parameters are configured for an SRS resource set that includes the SRS resource and wherein determining the one or more power control parameters of the SRS resource comprises selecting the one or more power control parameters from the multiple options for the one or more power control parameters that are configured for the resource set.
 10. The method of claim 1, wherein the SRS resource is shared between a first TRP transmission and a second TRP transmission, wherein the UE applies an Orthogonal Cover Code (OCC) to the SRS to maintain orthogonality in use of the SRS resource between the first TRP transmission and the second TRP transmission.
 11. The method of claim 10, wherein the first TRP transmission is sent from the UE to a particular TRP and the second TRP transmission is sent from a second UE to the particular TRP.
 12. The method of claim 11, wherein a third TRP transmission sent is sent from the UE to a second TRP, wherein the third TRP transmission is sent using a second resource comprising a same SRS base sequence as the SRS resource, wherein a cyclic shift is applied to the SRS base sequence for the third TRP transmission such that the second resource and the SRS resource are orthogonal.
 13. The method of claim 11, wherein a third TRP transmission sent is sent from the UE to a second TRP, wherein the third TRP transmission is sent using a second resource comprising a different SRS base sequence as the SRS resource.
 14. The method of claim 11, wherein a third TRP transmission sent is sent from the UE to a second TRP, wherein the third TRP transmission is sent using the SRS resource, wherein a comb structure, frequency hopping, or resource block-level partial frequency sounding structure is used to provide orthogonality between the third TRP transmission and the first TRP transmission.
 15. The method of claim 10, wherein the first TRP transmission is sent from the UE to a first TRP and the second TRP transmission is sent from the UE to a second TRP.
 16. The method of claim 10, wherein the UE applies the OCC to the SRS in response to receiving an indication from the gNB.
 17. A method comprising: determining, at a gNB that a plurality of TRP transmissions from one or more UEs are using a particular SRS resource; and in response to determining that the plurality of TRP transmissions from the one or more UEs are using a same resource, sending an indication to the one or more UEs which causes the one or more UEs to apply an orthogonal cover code (OCC) to the plurality of TRP transmissions.
 18. The method of claim 17, wherein: the plurality of TRP transmissions comprise a first TRP transmission from a first UE of the one or more UEs to a first TRP and a second TRP transmission from a second UE of the one or more UEs to the first TRP.
 19. The method of claim 18, wherein: a third TRP transmission from the first UE of the one or more UEs to a second TRP uses a second SRS resource comprising a same SRS base sequence as the particular SRS resource, wherein a cyclic shift is applied to the SRS base sequence for the third TRP transmission such that the second SRS resource and the particular SRS resource orthogonal.
 20. The method of claim 18, wherein: a third TRP transmission from the first UE of the one or more UEs to a second TRP uses a second SRS resource comprising a different SRS base sequence as the particular SRS resource.
 21. The method of claim 18, wherein: a third TRP transmission sent is sent from the first UE of the one or more UEs to a second TRP, wherein the third TRP transmission is sent using the particular SRS resource, wherein a comb structure, frequency hopping, or resource block-level partial frequency sounding structure is used to provide orthogonality between the third TRP transmission and the first TRP transmission.
 22. The method of claim 17, wherein: the plurality of TRP transmissions comprise a first TRP transmission from a first UE of the one or more UEs to a first TRP and a second TRP transmission from the first UE of the one or more UEs to a second TRP. 